I noticed that there is no option to blacklist biomes to prevent tree spawing. Sometimes they are in biomes where they shouldn't, e.g. some BOP biomes and Abyssalcraft.

Could this be added to the config? Black or whitelist?

Yeah, I dont see why not. In 1.13 I do plan on making all of the world gen a bit more configurable, but I don't really want to break the current world gen config in 1.12. Adding a simple blacklist should be possible without breaking things.

That would be nice. Thank you.

Added see bellow for an example ores.json config file:

https://gist.github.com/modmuss50/1768561b270c53085df63f19b19e658f#file-ores-json-L178-L181

just use the biome registry name to blacklist it.

That's great, thank you. :)