I would like to reserve a room for the initial meeting (in TUMonline) earlier than than the matching start. How is this possible?

It is not possible to reserve a room associated to your course in TUMonline earlier than decentralised planning start. Monday after "Dreikönig" for the  summer-semester and the first Monday after "Fronleichnam" for the  winter-semester). However, you can reserve a room using an “organizational date” in TUMonline. See link to scheduler for course organizers on:http://docmatching.in.tum.de/html/docmatching/index.php/scheduler-course-organizers