You can edit a group. You can for example remove a specific participant from a group. You click the symbol for your organization, choose Participants and then Groups. Click the name of the group you want to edit. The name of the group will appear to the right and under it, it says Edit group.
Click Edit group and you will see a list of all participants in the group. Remove a person by crossing her/him off the list and click the green button at the bottom to save.
