Under Advanced/Formatting/Artwork I have set up: ../Folder.jpg

Before 7.6.x this worked almost perfectly.

The scanner would look for "../Folder.jpg" first, then all the default filenames. With a directory structure like this:

ABBA - The Complete Studio Recordings/01 - ABBA - Ring Ring/Folder.jpg
ABBA - The Complete Studio Recordings/02 - ABBA - Waterloo/Folder.jpg
ABBA - The Complete Studio Recordings/Folder.jpg
(...)
Pink Floyd - Pulse/CD 1/Folder.jpg
Pink Floyd - Pulse/CD 2/Folder.jpg
(...)

in the first case (ABBA) it would find the generic artwork for the boxset, instead of the specific artwork for the individual albums. In the second case (Pink Floyd) it worked right out of the box.

The first case was fixed by replacing:
unshift @filestotry, $artwork;

with:
push @filestotry, $artwork;

in Slim/Music/Artwork.pm - in order to match the built-in filenames first, and only proceed to the custom filename if nothing was found. Permitting multiple filenames in the configuration would solve this as well, since one could just configure: Folder.jpg;../Folder.jpg

Anyway, since upgrading to 7.6.1 this custom filename doesn't work at all anymore. I'm allowed to save it, but it's like the scanner is rejecting the option completely, like it's not allowed to point to the parent directory?