Hi, many MC users including me are using an expression for the thumbnail text to grey out already watched episodes. I always wanted something like this for whole series/audiobooks/etc. However, I realized that there is an even better solution than greying out thumbnail text, because it only shows 0 or 100%, which is not quite sufficient for entries with multiple files.
A small progress bar that can be shown under or over the thumbnail text that indicates the percentage of the files in it that already have been played would be really nice. For instance if I have watched 7 of 20 episodes of some series, the progress bar would indicate a 35% progress.
This isn't a big or difficult feature, but a quite nice one because it encourages users to finish their tons of unwatched tv shows and unlistened audiobooks and therefore spend more time using MC. It also gives people the feeling to have achieved something, which is always nice.
Edit: Here is a little mockup to give an idea how it could look like: