I live the new Zoom feature to be able to switch between breakout rooms. You have to be on the latest zoom and the feature has to be enabled for your meeting.
After clicking breakout rooms at the bottom, you see the choices along with who is in each room. The trick is mousing over the number. If I mouse over “5”, it turns into the word join.
You can join a breakout from either the main room or another breakout. And you can always go back to the main room by clicking “leave breakout room.”
This is far better than my hack of joining as my computer, iPad and iPhone and switching physical devices. It also lets the team know which session I am actually paying attention too!