I have a Mac running PMMP. I want to serve up a second world. Can the existing server instance do that? Or do I simply make a duplicate directory, and run another instance of PMMP with a different port number? Thanks.
PMMP does have support for multiple worlds, however, you have to install an additional plugin (such as ManyWorlds) to take advantage of it.
You don't have for the pure loading of worlds. For teleportation however you do have to use a plugin. auto loading worlds the easy way: https://github.com/pmmp/PocketMine-MP/blob/master/src/pocketmine/resources/pocketmine.yml#L193-L198
Updated link here for MC 1.18.30 https://github.com/pmmp/PocketMine-MP/blob/4.3.3/resources/pocketmine.yml#L207-L213