When trying to quit the application because a file takes a long time to load that doesn't seem to be possible (without using taskmanager) as Designer asks us to wait for the load to finish.
IMO it should always close the application, no matter what's currently busy. Especially because one of the reasons to close the application could be to not wanting to wait for a large file to finish (or might be stuck forever).
Please make Affinity close immediately when exiting to prevent us needing to use the taskmanager to do so!