Library adjustments

How do I delete a folder from the library

See Wiki “Editing libraries”
https://support.plex.tv/hc/en-us/articles/200289266-Editing-Libraries
It may not be clear, but, you load up your Plex Web to get to the edit section, then click ‘Add folders’. To the right of the folders you have listed in the library is an “x” - that removes that folder from that specific library.
(It won’t delete files)