Hi Melissa,
Understood. This is not possible unfortunately, the plugin needs to read a list of planned webinar events from a specific extension in order to get this done. Groups do not contain such information because they are not a separate entity like an extension is, hence they are not compatible with the way the plugin was designed.
I can propose an alternative in case it works for you, to create a separate extension for Webinar management, which your group of users can share if they want it all under one roof. They just log in to the webclient with those credentials to manage or conduct the webinars as needed.