When you are the meeting host (star icon) you have the ability to create, duplicate or switch between active models for everyone in that session. All the Pro or Enterprise Users participating the meeting can ask to become the meeting host by pressing the star icon behind their name in the meeting panel.
Models shown in the Model viewer are placed at a slight offset to the locally stored models when in a multi-user session. Only these models will be visible to other users in a meeting. The meeting host can make new models or duplicates of the existing model to explore alternatives. Locally created models can also be shared with your coworkers by selecting that model (yellow highlight) and pressing the share button. Models shared will become active in a meeting to all participants and a copy of the previous model is made for every user in the meeting.
Models created in a meeting cannot be deleted until the meeting is ended. After this, the files you worked on with your team will automatically be converted to locally saved models that can be further edited, copied or deleted.