I'm trying to add blocks to the blacklist, but I can't seem to find where that is, nor will the mod tell me where. I'm using Biome's O' Plenty, and need to add custom rules to my game in order to make things work correctly. When ever I look into others issues, people are like "Add it to the blocklist", but I CAN'T FIND IT lol.

The block list for what things a storm or tornado can pick up is found under Tornado.CFG in the Weather2 folder. This is the part you are looking for:

# Enable GrabCond_List to use, add registered block names to list, use commas to separate values
S:Storm_Tornado_GrabList=planks, leaves

# Treat block grab list as a blacklist instead of whitelist
B:Storm_Tornado_GrabListBlacklistMode=false