Why?
Edit…I ran across this old post reporting that digikam removed metadata editing due to raw file corruption in version 5.8 (5½ years ago). So I guess that digikam will not do that.
I have also never used digikam sidecar files, Raw Therapee also adds sidecar files and I’m in the middle of learning Darktable/Ansel, which makes even more sidecar files, and I have no idea if those would conflict with Digikams, so I am hesitant to add any more sidecars.
I guess I will write a script using exiftool.
2nd (last?) edit:
It seems that Exiftool has a way to do this pretty easily with one command.