Hi @CCasey thank you for your post here on the Zoom Community! Yes, you can open and close Breakout (BO) Rooms during the same meeting, and each time you can reconfigure things like how many rooms you have and such. With our newer client versions (5.9.0 and above) you can even adjust BO Rooms while they are open, such as add participants to rooms, rename rooms, delete rooms, etc.
This support article talks about the possibilities https://support.zoom.us/hc/en-us/articles/206476313-Managing-Breakout-Rooms
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