Panelists talking issue

I'm the organizer and I'd like to communicate with other panelists as well as presenter before we actually start the webinar and talk to attendees.

Therefore, I'm wondering if it is possible that all panelists can talk to each other ( and maybe see each other) without being heard or seen by the attendees.

I've tried in the control panel but all I can do is mute/unmute others and myself.

Does anybody know how to keep the talking voice only in panelists?

We don't want attendees to hear our pre-meeting discussion.

Thank you.