How to add a button to a pre-existing tab on ribbon (C#)?

Question

I\'ve successfully created a new tab and put it next to the pre-existing ones. Then I realized that I\'ll only have one button on it, so it makes more sense (for now) to put it

Answer 1

If you just want a button to appear in an existing ribbon, in Visual Studio, here https://msdn.microsoft.com/en-us/library/bb608628.aspx#Anchor_2

in your case change the OfficeId to TabMail