Get rid of missing files

Ardour 5.12 The problem isn’t new and the region management improved, but I imported by mistake a lot of audio files into the region list. I used “remove unused”. So far so good. Later I deleted some files, to keep at least a little bit order. And when starting the project ardour complained about the missing files. From 4.7 I know how to edit the *.ardour file and I know that is a violation of the ardour code of usage. But that shouldn’d be necessary. There should be a way to get rid of unused files. At own risk of course