ADDING CUSTOM BLOCKS TO BIOMES (1.20.1)

[MoyshaKing]

so can anyone explain how to add custom features to biomes, i've been trying to make my a custom mushroom that spawns in the forest but nothing works. I've seen so many different ways on how people do that and I am completely lost now. 

[InvictusSlayer]

The most straightforward approach would be to use a feature biomemodifier - the wiki explains how to use these in full