Thank you, Stefan and Paul, for looking through the log file and for the additional advice!
Applying the default playback template didn’t change anything. I tried to save again and looked into the temporary folder. Unfortunately, the time of the score and scorelibrary files is 19:25, which is about the last time I managed to save successfully.
Then I opened a new project and copied the music there (no crash). But, funnily, in this new project, Dorico doesn’t react at all when I try to save or “save as…”.
But, this is weird: over here the export submenu looks like this – no MusXML to choose:
I guess I will have to input the flow again. Never mind, it’s not the end of the world.
Thanks for your support again! At this time of day… it has been said many times on this forum, but the user support of the Dorico team is truly astonishing!