Are you talking about using the supervision API? It is possible to create a multiple supervisors for a call monitoring group. Login your account at https://service.ringcentral.com then create a Call Monitoring Group, where you can select multiple users (that can monitor)

Read this blog for more information about how to monitor a call.

I'm asking for the ability for more than one person at a time to join a call that is in progress. When a second person tries to join the call they are blocked out.

Is there a way for this to be developed?

Ringcentral refers to the barge, whisper, take over, silent features as "call monitoring" https://support.ringcentral.com/s/article/8086?language=en_US . So I'm not really sure why it's confusing when users refer to it as such.

If you remember older home phones when someone was on a phone call another person could listen to that phone call by picking up another phone that was connected to that same phone line, but in this case we would want multiple people to be able to do so. As of right now only one person could do so. Many organization have been asking for the ability for multiple people to join in.

The conference line would not make sense in this situation because if someone calls a users direct line and the user wants the coworkers to listen in, they are not going to tell the caller to hang up so they can use the conference number.

This might not be the right forum to get this implemented, but people have been trying in the regular community board for years and it hasn't gotten anywhere, so it is worth the try.