In previous versions of Bridge there was a way to pull the list of Workspaces on the top of the window to the left. This would expose most of the saved workspaces so they could be re-ordered. in 2019 there is no way to expose more than just a few of the workspaces. When Bridge updated from 2018 the custom workspaces I set up from 1-5 were reordered down the list. Since the list can't be expanded, I can't out them in the order I had and use the Command-Fkey shortcuts.
I'm sorry you do not see the UI element from Bridge 8.1 that is missing in 9.1 (see arrow) which allows a user to extend the visibility of saved workspaces so they can be re-ordered easily and chosen faster than the drop-down.
Sure, by all means I'd be happy to spend even more of my time explaining about some feature that was arbitrarily changed for the worse on another forum which may or may not result in its function being addressed in a future release.