The cohosts of a meeting should be something that can be modified on a meeting regardless of where the meeting was created. Right now, if a meeting is created via the Outlook plugin, the cohosts need to be modified through that same plugin - they cannot be modified in the Webex web interface.
This is primarily needed for us when users are suddenly/unexpectedly OoO - but there's no administrative way to manage this, today.
If the meeting originates from Outlook, then you need to use Exchange Delegate controls to allow other people to edit the original booking owner’s meeting invitation. We believe that this Idea already exists, just not in the exact form of the request.
Making changes to the user’s calendar from Webex Site into Exchange would bypass the security & delegate controls of Exchange. In addition, the Page does not have the correct connectivity to update the meeting in Exchange or Exchange Online.