Only participants included in the Buzz as an Owner or Author can edit a Buzz.
As of the Buzzy v5 app (released late July 2019), editing or authoring a Buzz requires the app to be switched to Classic View. While in a Buzz you have editing permissions on, press the ‘Options’ button (the 3-dot icon at top right), then press the ‘Edit’ option. Your Buzz will open in a Buzzy Classic view and you can edit it as before. Once you’re done, simply close the Classic view by clicking the ‘x’ icon at the top left.