Make sure you go to your Settings of your Plex server and check the deletion box. As long as you are logged into the admin account on any of the Plex Amp clients, track deletion should be accessible.
with the recent update of PlexAmp 9.2.1, I’ve noticed no options to delete any tracks from anywhere but the Album level, despite having my media deletion box checked, regardless of client platform. It looks like single track deletion has been removed. This was not the case in the previous 9.2 build.
9.2.1 doesn’t seem to have no menu item for deletion on windows, iOS, and Android versions.