i still use rhino 3.0 for some tasks because there is a plugin i still use.
I recall from ancient history  that there was a workaround for the issue where the toolbars didnt stack properly.
the issue is that at some point, the toolbars only permit you to have one toolbar in each row, so a toolbar with a single button will occupy an entire line.
the workaround was that a certain file had to be deleted, and then the toolbars would allow you to stack them again.
if anyone could help it would be terrific, and miraculous. If i recall, a fellow by the name of Nikko Oksaanen or something like that nutted out the solution.
best regards from the early 2000’s,