Yes
https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/commits/9294ebbf051ad7340d7e37265568884439973a4a
SPIGOT-5877

Are you sure about this? I made a PR for this nearly a year ago and I can't see anything remotely similar in upstream. Unless it's handled somewhere outside of CraftServer and/or WorldCreator?

Support for this was added months ago

Any updates on this?

Ah ok in the future make sure you mention that on the ticket so we dont have developer overlapping PR's

@TheCreeperCow I have already made a PR, it just hasn't been merged yet. 736

Ill investigate this feature request as it seems there is a lot of interest in it however i cannot make any promises 

I don't expect this to be implemented right away. Does anyone know if there are tools to modify an existing world's biomes with datapack ones in the meantime?

I've made a plugin that can load custom dimensions as worlds, it seems to work so far, of course, if another plugin checks the biome type or something like that might break but I haven't run into issues yet (so use at your own risk): https://www.spigotmc.org/resources/1-16-custom-dimensions.83731/

This would be amazing to add support, especially for custom biomes. I hope it's something we can see in the near future! 

How does this WorldCreator thing work? Is it a plugin? I was looking into it and I am very confused. How can I use this?

I have implemented the ability to load generator settings via WorldCreator: 736. I have also outlined why the Biome class should be updated regardless if the class is implemented. tl;dr you can already import worlds that use the new datapack configuration system, without the need fot this.

@Tucker that's not harsh it is realistic. It would be a cool addition no doubt but as long as no one coming up with an API design for that, that will be stable enough for future, nothing will be implemented. The big thing here is that Mojang developers themselves declaring this feature as likely to change drastically. So supporting a feature, that is likely to change drastically, in an API needs more than just copying stuff present.

First step could be that the Biome enum is migrated to a class, keeping binary compatibility like the Bungee ChatColor, so that it could handle dynamic biomes with namespaced keys.
https://gist.github.com/yannicklamprecht/8cf3eb71c7ae66f7d88c863ebc03b2cb

Designing the Builder or especially the class that represents the Biome config is a whole other thing.

Sorry if I was complaining. Asking around, everyone I have asked is making it out to be like this feature will never be supported, so I've been getting progressively more and more worried with each response.

That's a pretty harsh response considering we've been nothing but polite about it. 

We don't know to implement this stuff, that's why we come to you. That's why we use Spigot. We can't do things like this. We rely on Spigot and it's features.. Telling us to do it ourselves just kinda feels like you're spitting in our face about it. The guy who first started this ticket presented ways to do it - granted, I don't know if it's correct or not, but it looks pretty legit to me.

I read the 1.16 expectations and well.. I don't feel like that applies to us. I don't expect anything, hell, Spigot could shut down at any moment, but requesting an important feature to be added is different. That's not expectations.

No one has straight up said it's not going to be implemented. If it's so easy or important to you why don't you implement it yourself and PR it so everyone can benefit? Hint: because it's hard to do properly. We get the point, you want the feature, but moaning and complaining isn't going to get it implemented. I suggest you refer to the 1.16 announcement regarding expections.

Yes, please add support for this. I delayed updating my server to 1.16 because I had many plans for this feature. Now everything that's been teased to the community can't be implemented and I've done a bunch of work for nothing.
Mojang is probably going to continue to update the world format anyways, so getting behind now will probably mean more work for 1.17

Exactly, this hurts no one by adding support for it, if it breaks that's on us, we're the ones relying on it. A lot of people were banking on these features and for Spigot to come out and say they straight up aren't going to support it is really disappointing, considering there really are no other options out there.

It will be really important for every server especially because the new Custom Biomes support custom Foliage/Sky/Water Tints. And only because it is experimental it doesn't mean people don't want to use it. I mean it doesn't hurt anyone, right?

This needs to be added, needs. Even if it's experimental, just add the support for them! If it's removed later or broken later, we'll just have to deal with it.

I was actually really excited to use the custom dimensions for my server. I want to continue to provide a unique, fun game-play experiences whenever possible. I saw this as a great way to do that and promised my server custom dimensions. I hope it's still planned to be implemented soon. Was the main feature in the 1.16.2 update. 

Plus the other updated modded server platforms have them implemented. (But those require client side mods so almost no one uses those)

The details may change but custom biomes will stay. So it would be great if they were supported by spigot.

Among other issues these features are labelled experimental by Mojang