Ability to specify lens when not present in EXIF
I occasionally use a Samyang 300mm reflex lens with my Olympus OM-D E-M10III camera. This lens is a "dumb" lens and does not communicate with the camera electronically. I have created and filed upstream appropriate calibration data, but it is cumbersome to apply it within darktable. It would be very nice if I could select photos that I know were taken with this lens (currently everything without an EXIF spec but in general by hand) and set the EXIF information to contain which lens I used. Then simply turning on "lens correction" would do the right thing for all photos.
As it currently stands, I can turn on lens correction for a photo taken with this lens, then specify the lens, the focal length (always 300mm but defaults to zero) and the f-stop (always 6.3 but defaults to zero), and the image is corrected (most importantly the vignetting). I can then copy this lens correction item and paste it on all relevant photos. But if I accidentally paste it on a photo that was taken with a different lens, that photo is corrected as if it were taken with my dumb lens. Undoing this operation requires, as far as I can tell, going back in the history to before lens correction was applied (turning it off does not work) and turn on lens correction, restoring autodetection. There is no obvious way, in the lens correction widget, to specify whether the lens was user selected or autodetected - not relevant for this image but relevant if you want to paste it elsewhere.