You can do that on the ÖBB website:

Or at a ticket office of course.

 @rvdborgt thanks for the super soon reply! And what about Zuerich Hb (Switzerland), is it possible to do so online for it, too? Thank you tons in advance! :)

Yes also possible via ÖBB

This night train has portions/cars for several destinations-that is one big advantage of old-style trains above planes or buses-the cars can change and added to other trains.

What works out best for this trip depends on timings and the actual place. I think probably via München. There are also for some time WORKs along the austrian section west of Innsbruck where the Swiss train has to pass by and that may mean diversion or temporary cancellation.

BTW-if you ONLY want to make this return its likely cheaper to simply book advance tickets via bahn.com or oebb for the dates you want to go.