How to change library paths to use UNC names instead of drive letters?

@alekdavis said:
What I meant was that my original question was not about how to enter (type in/copypaste/etc) the UNC path in the settings. It was about the process of changing the already existing drive-based path to the UNC-based path pointing to the same location without breaking metadata in the library.

If you are feeling particularly adventurous, you can even save the part of updating the library and then remove the duplicates.
Because if you did a lot of customization and/or used ‘Fix Match’ all the time, you will get a high number of mismatches.

This procedure changes the paths to the media items directly in the database.
Try this only if you have a working backup of the plex database!