I was experimenting with this exact thing on a smaller library I have. I found that when I deleted my existing collections, Plex LOCKED the collections field as blank and wouldn’t update that field. I had to go into each movie individually and unlock the blank Collections field. Once that was done (437 entries) then I did a Metadata Refresh and it refilled the collections as I expected. Not a fun solution.
I’m going to try creating a new library with the same settings and see if it ‘upgrades’ the library to the new movie agent collections correctly THEN go back in and add the specialized collections that I want. That should also keep my watched status for the library.
It would be nice if Plex had two fields for collections, Source and Personal. Source would be the Plex Source for collection metadata and NOT be modifiable. The Personal would let you add collections to your hearts desire. Then let you select whether you use the Source and/or Personal collections for that library.
Many thanks for pointing that out to me @CWallace. You’re right that doesn’t sound like a fun solution, albeit, that’s what I’ll do!
Before I run head first into going through my equally large amount of entries, I’m going to have a quick google tomorrow if there is a way to bulk edit that field within Plex.
There is, you can multi-select items in the Web interface. When you hover over a movie poster you’ll see a little circle in the top left corner, you can select the start item like this and then while holding the shift key select the last item and it will select the range.
Once you’ve selected the range you will see that there is a pencil icon in the bar at the top, selecting this will allow you to edit multiple fields.
Some caveats, you can only select multi-select edit items of the same type so if you have collections enabled alongside your movies you’ll have to not select those or disable that in the library settings. Also some of the collection tags will be locked and some won’t so you’ll have to first lock all of them, save, then edit and unlock the collections tag and save again.