Screenshot / Code Snippet
This script adds a link to rejoin favorite chatrooms, even if you're in multiple ones already:
When you're in only one chatroom on a server, there's an orange button which you can use to quickly join all your favorite chatrooms:
However, that button disappears if you're in two or more rooms. This script brings back that functionality.
Tested with Violentmonkey in Firefox on macOS, but it's likely to work on all browsers and platforms. (Please let me know if it doesn't!)
Post a comment or answer here, or create an issue/pull request on GitHub.