Create a Custom Tab - ribbon

Question

When I start a new Excel Web Add-in, by default the blank project has a MyAppName.xml file that declares the ribbon.
The declaration sets a custom group and a custom control under the native Home Excel tab.
What I want is to create a separate tab for my Addin.
In the file project itself, there are these code lines:
<!-- Use OfficeTab to extend an existing Tab. Use CustomTab to create a new tab. -->
<OfficeTab id="TabHome">
So I changed OfficeTab for CustomTab, but now I get the message in the error list:
The element 'CustomTab' in namespace 'http://schemas.microsoft.com/office/taskpaneappversionoverrides' has incomplete content. List of possible elements expected: 'Group, Label' in namespace 'http://schemas.microsoft.com/office/taskpaneappversionoverrides'.
Do you know how I can create a custom tab? What am I doing wrong?
I'm using:
Microsoft Visual Studio Enterprise 2017
Version 15.2 (26430.12) Release
VisualStudio.15.Release/15.2.0+26430.12
Thanks.

Answer 1

Below is an example manifest that uses CustomTab. Can you compare your's with the example and see what might be different? Are you giving the CustomTab a unique ID? Does it have Group and Label child elements?
<?xml version="1.0" encoding="utf-8"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0" xmlns:ov="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="TaskPaneApp">
<!-- See https://github.com/OfficeDev/Office-Add-in-Commands-Samples for documentation-->
<!-- BeginBasicSettings: Add-in metadata, used for all versions of Office unless override provided -->
<!--IMPORTANT! Id must be unique for your add-in. If you copy this manifest ensure that you change this id to your own GUID. -->
<Id>e504fb41-a92a-4526-b101-542f357b7acb</Id>
<Version>1.0.0.0</Version>
<ProviderName>Contoso</ProviderName>
<DefaultLocale>en-US</DefaultLocale>
<!-- The display name of your add-in. Used on the store and various placed of the Office UI such as the add-ins dialog -->
<DisplayName DefaultValue="Add-in Commands Sample" />
<Description DefaultValue="Sample that illustrates add-in commands basic control types and actions" />
<!--Icon for your add-in. Used on installation screens and the add-ins dialog -->
<IconUrl DefaultValue="https://contoso.com/assets/icon-32.png" />
<HighResolutionIconUrl DefaultValue="https://contoso.com/assets/hi-res-icon.png" />
<SupportUrl DefaultValue="[Insert the URL of a page that provides support information for the app]" />
<!--BeginTaskpaneMode integration. Office 2013 and any client that doesn't understand commands will use this section.
This section will also be used if there are no VersionOverrides -->
<Hosts>
<Host Name="Document"/>
</Hosts>
<DefaultSettings>
<SourceLocation DefaultValue="https://commandsimple.azurewebsites.net/Taskpane.html" />
</DefaultSettings>
<!--EndTaskpaneMode integration -->
<Permissions>ReadWriteDocument</Permissions>
<!--BeginAddinCommandsMode integration-->
<VersionOverrides xmlns="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="VersionOverridesV1_0">
<Hosts>
<!--Each host can have a different set of commands. Cool huh!? -->
<!-- Workbook=Excel Document=Word Presentation=PowerPoint -->
<!-- Make sure the hosts you override match the hosts declared in the top section of the manifest -->
<Host xsi:type="Document">
<!-- Form factor. Currently only DesktopFormFactor is supported. We will add TabletFormFactor and PhoneFormFactor in the future-->
<DesktopFormFactor>
<!--Function file is an html page that includes the javascript where functions for ExecuteAction will be called.
Think of the FunctionFile as the "code behind" ExecuteFunction-->
<FunctionFile resid="Contoso.FunctionFile.Url" />
<!--PrimaryCommandSurface==Main Office app ribbon-->
<ExtensionPoint xsi:type="PrimaryCommandSurface">
<!--Use OfficeTab to extend an existing Tab. Use CustomTab to create a new tab -->
<!-- Documentation includes all the IDs currently tested to work -->
<CustomTab id="Contoso.Tab1">
<!--Group ID-->
<Group id="Contoso.Tab1.Group1">
<!--Label for your group. resid must point to a ShortString resource -->
<Label resid="Contoso.Tab1.GroupLabel" />
<Icon>
<!-- Sample Todo: Each size needs its own icon resource or it will look distorted when resized -->
<!--Icons. Required sizes: 16, 32, 80; optional: 20, 24, 40, 48, 64. You should provide as many sizes as possible for a great user experience. -->
<!--Use PNG icons and remember that all URLs on the resources section must use HTTPS -->
<bt:Image size="16" resid="Contoso.TaskpaneButton.Icon16" />
<bt:Image size="32" resid="Contoso.TaskpaneButton.Icon32" />
<bt:Image size="80" resid="Contoso.TaskpaneButton.Icon80" />
</Icon>
<!--Control. It can be of type "Button" or "Menu" -->
<Control xsi:type="Button" id="Contoso.FunctionButton">
<!--Label for your button. resid must point to a ShortString resource -->
<Label resid="Contoso.FunctionButton.Label" />
<Supertip>
<!--ToolTip title. resid must point to a ShortString resource -->
<Title resid="Contoso.FunctionButton.Label" />
<!--ToolTip description. resid must point to a LongString resource -->
<Description resid="Contoso.FunctionButton.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.FunctionButton.Icon16" />
<bt:Image size="32" resid="Contoso.FunctionButton.Icon32" />
<bt:Image size="80" resid="Contoso.FunctionButton.Icon80" />
</Icon>
<!--This is what happens when the command is triggered (E.g. click on the Ribbon). Supported actions are ExecuteFunction or ShowTaskpane-->
<!--Look at the FunctionFile.html page for reference on how to implement the function -->
<Action xsi:type="ExecuteFunction">
<!--Name of the function to call. This function needs to exist in the global DOM namespace of the function file-->
<FunctionName>writeText</FunctionName>
</Action>
</Control>
<Control xsi:type="Button" id="Contoso.TaskpaneButton">
<Label resid="Contoso.TaskpaneButton.Label" />
<Supertip>
<Title resid="Contoso.TaskpaneButton.Label" />
<Description resid="Contoso.TaskpaneButton.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.TaskpaneButton.Icon16" />
<bt:Image size="32" resid="Contoso.TaskpaneButton.Icon32" />
<bt:Image size="80" resid="Contoso.TaskpaneButton.Icon80" />
</Icon>
<Action xsi:type="ShowTaskpane">
<TaskpaneId>Button2Id1</TaskpaneId>
<!--Provide a url resource id for the location that will be displayed on the task pane -->
<SourceLocation resid="Contoso.Taskpane1.Url" />
</Action>
</Control>
<!-- Menu example -->
<Control xsi:type="Menu" id="Contoso.Menu">
<Label resid="Contoso.Dropdown.Label" />
<Supertip>
<Title resid="Contoso.Dropdown.Label" />
<Description resid="Contoso.Dropdown.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.TaskpaneButton.Icon16" />
<bt:Image size="32" resid="Contoso.TaskpaneButton.Icon32" />
<bt:Image size="80" resid="Contoso.TaskpaneButton.Icon80" />
</Icon>
<Items>
<Item id="Contoso.Menu.Item1">
<Label resid="Contoso.Item1.Label"/>
<Supertip>
<Title resid="Contoso.Item1.Label" />
<Description resid="Contoso.Item1.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.TaskpaneButton.Icon16" />
<bt:Image size="32" resid="Contoso.TaskpaneButton.Icon32" />
<bt:Image size="80" resid="Contoso.TaskpaneButton.Icon80" />
</Icon>
<Action xsi:type="ShowTaskpane">
<TaskpaneId>MyTaskPaneID1</TaskpaneId>
<SourceLocation resid="Contoso.Taskpane1.Url" />
</Action>
</Item>
<Item id="Contoso.Menu.Item2">
<Label resid="Contoso.Item2.Label"/>
<Supertip>
<Title resid="Contoso.Item2.Label" />
<Description resid="Contoso.Item2.Tooltip" />
</Supertip>
<Icon>
<bt:Image size="16" resid="Contoso.TaskpaneButton.Icon16" />
<bt:Image size="32" resid="Contoso.TaskpaneButton.Icon32" />
<bt:Image size="80" resid="Contoso.TaskpaneButton.Icon80" />
</Icon>
<Action xsi:type="ShowTaskpane">
<TaskpaneId>MyTaskPaneID2</TaskpaneId>
<SourceLocation resid="Contoso.Taskpane2.Url" />
</Action>
</Item>
</Items>
</Control>
</Group>
<!-- Label of your tab -->
<!-- If validating with XSD it needs to be at the end -->
<Label resid="Contoso.Tab1.TabLabel" />
</CustomTab>
</ExtensionPoint>
</DesktopFormFactor>
</Host>
</Hosts>
<Resources>
<bt:Images>
<bt:Image id="Contoso.TaskpaneButton.Icon16" DefaultValue="https://myCDN/Images/Button16x16.png" />
<bt:Image id="Contoso.TaskpaneButton.Icon32" DefaultValue="https://myCDN/Images/Button32x32.png" />
<bt:Image id="Contoso.TaskpaneButton.Icon80" DefaultValue="https://myCDN/Images/Button80x80.png" />
<bt:Image id="Contoso.FunctionButton.Icon" DefaultValue="https://myCDN/Images/ButtonFunction.png" />
</bt:Images>
<bt:Urls>
<bt:Url id="Contoso.FunctionFile.Url" DefaultValue="https://commandsimple.azurewebsites.net/FunctionFile.html" />
<bt:Url id="Contoso.Taskpane1.Url" DefaultValue="https://commandsimple.azurewebsites.net/Taskpane.html" />
<bt:Url id="Contoso.Taskpane2.Url" DefaultValue="https://commandsimple.azurewebsites.net/Taskpane2.html" />
</bt:Urls>
<bt:ShortStrings>
<bt:String id="Contoso.FunctionButton.Label" DefaultValue="Execute Function" />
<bt:String id="Contoso.TaskpaneButton.Label" DefaultValue="Show Taskpane" />
<bt:String id="Contoso.Dropdown.Label" DefaultValue="Dropdown" />
<bt:String id="Contoso.Item1.Label" DefaultValue="Show Taskpane 1" />
<bt:String id="Contoso.Item2.Label" DefaultValue="Show Taskpane 2" />
<bt:String id="Contoso.Tab1.GroupLabel" DefaultValue="Test Group" />
<bt:String id="Contoso.Tab1.TabLabel" DefaultValue="Test Tab" />
</bt:ShortStrings>
<bt:LongStrings>
<bt:String id="Contoso.FunctionButton.Tooltip" DefaultValue="Click to Execute Function" />
<bt:String id="Contoso.TaskpaneButton.Tooltip" DefaultValue="Click to Show a Taskpane" />
<bt:String id="Contoso.Dropdown.Tooltip" DefaultValue="Click to Show Options on this Menu" />
<bt:String id="Contoso.Item1.Tooltip" DefaultValue="Click to Show Taskpane1" />
<bt:String id="Contoso.Item2.Tooltip" DefaultValue="Click to Show Taskpane2" />
</bt:LongStrings>
</Resources>
</VersionOverrides>
</OfficeApp>
See also this article and the samples it links to. And check out Validate and Troubleshoot your Manifest too.