When using Cubase 11 in hiDPI mode, the project window will just resize on performing certain actions, like opening a sampler track. Turning off HiDPI mode will stop the behaviour. Opening some plugins also causes the behaviour. Sampler track is basically unusable for me right now because I have to keep maximising the window everytime I select a sampler track or open one.
Thanks Martin, hopefully it will get fixed in the next update, pretty glaring bug!