A text file(s) with a list of links. Use LibRedirect or some other redirector extension to redirect the links to the instance of your choosing, just change the redirector when you want to change instances.
Also- Couldn’t you add ‘groups’ to your current setup by just creating folders in your existing bookmarks? (assuming you’re using bookmarks that are baked into your browser)
I haven’t used; but I’ve also heard of sprays with a bitter taste to make cat’s not want to chew on things.