So, I copied two buttons from default into a custom toolbar - Project and Pull. Both have left and right button commands, the right buttons being the “Loose” option on both.
As I find the icons are too similar, I decided to use text-only buttons, so I simply checked text only in the button editor and changed the command names.
I then closed Rhino and re-opened it, and this is what I found:
The left macro is gone on both.
This most likely that despite what we have been previously told, making a copy of a button does not create a new independent one unlinked from the original. So, when I modified the name in order to have the text the way I wanted (shorter and in caps), it killed the macro link. Even replacing the original Pull with PULL did it.