Not to take away from the feature request but just as an FYI, which is also mentioned in the other thread @Harmon758 linked above, the closest feature we currently have to dropping is to Hide the show from your Progress (and additionally Calendar) which will essentially stop it from showing up in those sections but keep your history in tact (otherwise, not that I suggest doing this, but you could delete the history and leave it at that).
Look for the 
icons in those Progress/Calendar sections. On iOS and Android you can hide from both at once via; long pressing the episode in Up Next, or the in the Profile’s Progress tab, and then look for ‘Hide Show from Show Progress and Calendar’ options.
