I finally managed to set up a simple custom dimension, but now what I'm wondering is how to move a player from the overworld to this dimension.

 

I tried using player.travelToDimension() but this method, immediately after loading the dimension, unloaded it and teleported me to the nether.

 

So how should I go about doing this?

You should use:

 

entityPlayerMPObject.mcServer.getConfigurationManager().transferPlayerToDimension(entityPlayerMPObject, dimensionID, new CustomDimensionTeleporter(entityPlayerMPObject.mcServer.worldServerForDimension(dimensionID)));

 

Of course, this requires a Teleporter class for your custom dimension. Just take a look at the Teleporter class in net.minecraft.world and make your own class that extends that Other than that entityPlayerMPObject is just an object of EntityPlayerMP and dimensionID is obviously the dimension's ID

 

 

From what I can tell player.travelToDimension() only works for travelling to the Nether for whatever reason.