Not sure if JEI works the same, but REI shows all the game's compostable items. It still shows that it results in bone meal. If possible it should have compatibility with your mod and show dirt!

Well here is the score.

I ended up going in the opposite direction and made Compost more complex by adding JSON configurability, which means you can produce whatever items you want!

I chose to cancel out the default bone meal spawning so you could choose to have it if you wish.

Figuring out how to add these as a plugin for REI was pretty straight forward, but the thing is in its default client plugin it registers the bone meal for the compostables, and I don't believe there is a way to remove that asides from mixing into it. If there is a better way, I guess that can come in the future, but for now it will be as so!

Actually recently it was revealed to me that this mod breaks Farmer villagers. So my bandage solution is to simplify this simple mod even further and just make it so it adds a dirt block into what drops with the bone meal, which I suppose works like you are getting the rich humus soil and its fertilizing qualities. Anyways, that should satisfy all parties involved, and regardless of how it ends up deploying should make this issue moot.

I noticed today that the REI plugin was not parsing entries with NBT properly, causing them to not appear. I will look further into this and attempt to fix it, will probably be all that comes in the next version unless I can crack the hopper output issue.