Add ability to have GoToAssist Service Desk customers add email addresses to their watchlist

Currently there is no way in the GotoAssist Service Desk portal for a customer to add someone to their watchlist on a ticket.  The technician has to do that for the customer.  This is a real pain.  Why can't the service desk portal give the customer the ability to add an email address to the watchlist of their ticket?  This seems to be so elementary I can't believe it isn't there already.