Minecraft crashed when I tried to teleport to the "Overworld". I used JED to set the Initial Spawn Dimension to id 2. Then I used the command /tpj 0 to teleport to Dimension 0 which should be a Lost City World. In the World creation GUI I selected the "The Lost Cities" Worldtype but also used the JED dimensions.json to override Dimension 0 with "lostcities" Worldtype.

I'm sorry if I made the mistake or if another mod caused the crash (mentioning @maruohon the JED dev)

crash-2017-06-09_20.54.50-server.txt

dimensions.json

Overriding the overworld (specifically dimension 0) might have some (more) issues that overriding the Nether or the End for example. So I would try not overriding the overworld, unless it's simply necessary for something you want to achieve. It might be safer just setting up the lost cities as a custom dimension, and maybe simply "lock out" the regular overworld (disable teleporting to, and set the respawn dimension ids to something else), if you don't want the regular overworld to be accessible in addition to the Lost Cities and the other dimensions.

Based on your dimensions.json config, it seems that you mostly want to raise the cloud height and disable respawning in the lost cities world. It should also be noted that setting keeploaded: false for dimension 0 is a bad idea since lots of vanilla code expects it to always be loaded, but I think I'm force setting it to true for dimension 0 in JED anyway.

Thanks for your answer. My goal is to have a Garden of Glass dimension as the initial spawn and the respawn dimension and additionally a Lost Cities dimension. Ideally, I would then use the World Drop mod (no 1.11.2 version) to teleport between them. The cloud height was just a bonus to indicate that the Garden of Glass is above the Lost City.
I didn't test yet if I can build a Nether Portal in another dimension than the Overworld but I guess not, that is why I have the Lost City as Dimension 0.
I also don't know if I can change the Nether with JED to what I would like to have. I would like to have an infinite Lava Ocean with Nether Fortresses but I think the WorldProviderHell(JED) can't make flat worlds and the WorldProviderSurface(JED) doesn't generate Nether Fortresses, Lava flows slow and I can place Water.

I think you are correct in all counts. I could at least add support for selecting any of the vanilla ChunkProviders for use in any dimension. It should allow for at least a flat infinite-lava-ocean "Nether" dimension. If you want to talk more about this without clogging up this issue report, here is an invite to my Discord server: https://discorg.gg/2FgywHj