A workaround is to export your MediaMonkey M3U files to a folder.
Install iTunes on your Plex server (assuming you are in Windows). You have to set it up to not do any automatic arranging of your files, then import your library.
You may then import the playlists.
Then Plex can import your iTunes playlists.
It is clunky and I don't like putting iTunes anywhere, but it is clean and works with my playlists of thousands of tracks.

Be aware that the Plex/iTunes integration only works when both are installed in the default locations, so on "c:". Yuck. There is information on working around this, but it is the usual mess of editing config files and settings. I found it easier to wait until my next hardware rebuild and just do what it says.

I would love to pay money to buy (or even have an increased monthly fee) for a direct Plex plug-in to integrate Media Monkey. I have submitted to both companies with this request. If you agree, please go to both sites and submit requests.

That's not possible as Plex can't import Playlists. There may be some plugins for Plex that can add this functionality.

Mediamonkey has always been my digital jukebox. I've created a lot of M3u playlists of favorites. I'm going on a long trip and would like to have the ability to play my local media including playlists remotely over the internet. I've setup a Plex Media Server on my Windows computer and installed the Rasplex client on a Raspberry Pi to take on the road.

My problem is I can't see a way to get the Mediamonkey playlists to work with Plex Media Server. Please offer some help if you are able.