Situation:
Complication:
Any idea how we could achieve adding buttons?
We can request changes to the non-managed/VBA add-in.
VBA add-ins don't have their own namespace by default, but can have one. If you create a custom namespace, then multiple VBA add-ins can share the same tab on the ribbon, for example.
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui"
xmlns:nsMySpace="SomeName">
Then to create a new tab that other add-ins can share:
<tab idQ="nsMySpace:MySpace_Tab" label="MyTabLabel">