You should already be able to sort items in a playlist to your liking (e.g. chronologically).
There’s been a number of suggestions discussing options to import playlists or create playlists based on files, e.g. Option to use existing m3u for playlist feature
There’s an existing feature suggestion discussing an option to store the progress inside a playlist and being able to resume from where you left off. → Playlists - Remember position for subsequent resume
Plex drops items from a playlist that have been removed/deleted from Plex. If you replace a file, make sure to add the new file before deleting the old one – this way, Plex will link the new file to the existing library item and you won’t loose manual edits or playlist assignments.
