As a Meeting Host, to mute an individual or all participants at once:

  1. Select Participants from the quick access meeting controls to display the Participants Panel.
    Participants example
  2. Right-click on a participant from the Participants Panel.
  3. Select to either mute that individual or all participants.
    Mute individual or all participants example

Note:

Microphones can also be unmuted for an individual or all participants from this same menu.