When you create a new chat module instance you can select between its options whether to repeat the session. This chat instance creation impacts in the calendar events. When you create a new chat module instance an event in the calendar is created but when you decide to repeat the session that doesn't impact in the calendar. There is only one event created in the calendar.
I believe that if we copy the code from the form of an event and we put that code into the new chat module instance, and of course we do some logic in the chat_add_instance($chat) function in /mod/chat/lib.php we could get this done.