I've been creating child profiles for a box set, Tout(e) Varda, using the disc IDs for the individual discs. Everything was going smoothly until the last 2 discs, Agnès de ci de là Varda, whose disc IDs already show up in the database from an individual release. I could simply add that profile to the box set contents, but the artwork is different. (The box set version has its own keep case, with artwork specific to that title, but in a similar theme/layout to the other keep cases in the set.) What's the proper way to proceed here?

Pulling up the release when putting the disc in the drive happens for 2 reasons.  Download the existing individual profiles and find out which one it is.

It will pull them up if they were entered keyed with the Disc ID.  If this is the case you simply add the existing profiles to your box set and say in your notes that they were released previously as individual discs.

It will also pull up the profile if they were entered by UPC but the disc ID information is in the disc section of the profile.  If this is the case you can then change the UPC to the disc ID, change the artwork to match your release, and then submit the new, disc ID keyed profile.

Make sense?