So super new at Outlook add-in's but I have created a VSTO add-in in C# for Outlook that is working. The function it does is triggered by a button on the ribbon which is added to the Add-Ins section on startup. I would prefer this not be added automatically by the add-in as it is now and instead be a command the user would add through the customize ribbon action in Outlook. I can use the customize ribbon function in Outlook to add this command to other ribbons and groups but so far have not figured out how to not add it to a ribbon through the add-in code and still have it available to customize.
Currently the button is created via XML not the ribbon designer. I have not included any code here since I'm not sure that any is needed for this question or what it would be if so.
Try to add visible="false" attribute to the button.