Hello,
I haven’t found a way to do this yet but i wanted to ask here : maybe someone has 
How would you visualise your viewing progress with a bunch of media file? Ideally there would be some visual feedback in dolphins UI for a file that you can create after youve watched 5 out of 10 episodes and dont want to forget. I know its silly, but practically useful.
Maybe a darker colour or an icon on the file or anything that gives it an indication basically.
I vaguely remember KDE icons on the desktop having multiple buttons on them. Left would open the file, and right would open properties this could be several years ago) and it probably never survived 
You can attach a tag - but this is rather tedious and its not obvious unless youre in Details mode or unless you hover over the file.
Thanks.
you can add a 3rd party service menu that will let you easily change the folder color or icon to help you keep track.
ctrl+shift+, > context menu > add new…
the one i use is Color Folder and Custom Icon - KDE Store
You could also just right-click the folder, choose properties, then click on the icon (or the edit icon button) to change it to some other icon. You would decide what system you use to determine a watched episode.
@skyfishgoo’s is pretty useful too. You could use different colors to determine a number.
And another option is to place an empty file in the folder and call it the number of the last episode you watched.
i understand that the newer dolphin for plasma 6 actually has this feature built in now… i’m still on plasma 5 which is why i have to use the 3rd party plugin.
Yes, that is what I was referring to.
For me, colors wouldn’t work for a series with many episodes, so I’d actually go with my 3rd suggestion.
or sort by last access in dolphin