I came across an Excel add-in (.xlam) that appears to use VBA script to activate Ribbon groups. I would like to know how this is done.

Illustrated in more detail but simplified. The xlam file creates a new Ribbon tab with one Ribbon group containing one button.
If I click on this button additional ribbon groups are added to the Ribbon tab.

A look in the VBA Editor VBA project list shows that no file was opened by clicking the Ribbon button.
The Ribbon xml file of this xlam only contains the script for the one Ribbon tab, Ribbon group and button.

I have the impression that the script activated by the button calls in the additional Ribbon groups and buttons.
And this seems to work without opening another xlam file. I have no idea how that is done.

Can somebody explain to me how to do that?