The Microphone Controller button will appear on your non-drawing hand controller when in the Collab scene. Use this button to quickly Mute or Unmute the microphone.
Mute or Unmute the microphone by selecting the microphone button on your non-drawing hand controller. You can do this by clicking the button on the controller or by selecting it with the pointer on the drawing hand controller.
Before you enter the Collab room, make sure the app is granted Microphone permission. You'll be prompted to do this once you try to join the room or you can grant the permission before opening the app: select the three dots on the bottom right of the app tab > select Permissions > switch the toggle button to the right.