Thanks for the heads up! There were at least two old threads that asked for this. They were closed long ago for inactivity, but this feature request continues to come up.
Labels for Libraries @wesman
Plex Sharing Labels & Libraries @mtkeane
I’m confused by the pushback this request gets in different threads. The way labels work, the need to apply top-down labels to libraries has been explained fairly well, especially for managing kid-appropriate content across multiple libraries. Technically speaking, it doesn’t seem like a huge ask to add a text label field to libraries, but I’m no developer.
Can all 4 be collapsed or linked? It looks like those two above were created before voting was a thing.
(re: the second link you pasted. Maybe I’m missing something, but it seems to ask for functionality that is already present with labels – the ability to exclude/include specific items. Judging by the example provided, they’re not using labels correctly.)