Show mark as played for groups

Description

OP: https://forum.videolan.org/viewtopic.php?f=35&t=157345

Expected behavior

When files are Grouped by Name etc., they are represented by a single composite thumbnail with a label that says "N videos". However, at present simply by looking at that thumbnail there's no way to tell whether all the videos in that group have already been played or not. For that one has to currently click on the group's thumbnail first to display all the files inside, then see whether all their thumbnails have the white check mark on orange triangle or not.

So I'd like to propose that if all the files in a group have been played, then the group's combined thumbnail should also automatically display the white check mark on orange triangle. That way, a single glance at the top-level group thumbnail itself will suffice to know whether all the files in that group have been played already or not.

Screenshot / video

App mode

Smartphone