Right now there's no way to specify that the cover of https://bookbrainz.org/edition/b3ed75ea-9f74-44fa-833e-fa2c895c6b12 has "H. P. Lovecraft" on it. In this case, all works inside are written by him, so there's that at least, but there's definitely cases where only one author will be on the cover, yet the book will include work by others. And in any case, people will expect to be able to enter this info in a simple way.

I'm not sure if edition-groups should have credits too - MusicBrainz Release Groups have them, but it mostly duplicates release credits. On the other hand, it's useful in order to have a clear list of edition-groups to list under a creator.