Due to how you handle recipes, this mod is inherently incompatible with CraftTweaker's compost recipes.

@jaredlll08 can explain more in detail.

This may also affect some of your other mods too, albeit in other ways. I suggest looking them over.

No other way to do it I'm afraid. So probably wont change it.
Unless CraftTweaker dev has an ingenious way of doing this.

I'm not actually sure why this wouldn't be working, so for starters the actual issue is adding new compostables, which in CraftTweaker is done like so:

composter.setValue(<item:immersive_weathering:ivy>, 0.15);
composter.setValue(<item:immersive_weathering:weeds>, 0.15);

That simply adds to the net.minecraft.block.ComposterBlock#CHANCES map, which since you extend ComposterBlock, it should continue using right?

No other way to do it I'm afraid. So probably wont change it.

I'm assuming you are talking about this piece of code:
https://github.com/xanthian/variantcomposters/blob/1.19/src/main/java/net/xanthian/variantcomposters/mixin/RecipeManagerMixin.java#L26-L29

There shouldn't be any issue for CraftTweaker to change those recipes as we run long after your mixin is applied.

so a new plant/tree/food cannot be composted in the composters I add??
not sure how thats an issue on my side tbh, my composters extend ComposterBlock and dont do anything fancy other than copy the settings from the vanilla Composter
@Sunconure11 Can you elaborate further please, with error/screenshots where possible

Ah this is 1.19.
As of 1.20 I wont be using the recipe mixin anyway.

Also, please elaborate on what / how its incompatible

I believe the incompatibility is that setting new compostables doesn't actually do anything, I have not confirmed this, just going on what Sunconure11 has said.

Saying that, I don't see how this would be an issue on your side, my current guess is that another mod is messing with it.

Issue is also present when trying to do it with KubeJS.

We've come to the general conclusion that your mod is not at fault, but the bug is that stuff added in via CraftTweaker or KubeJS won't go into a composter.