I'm using create with the biome mod BYG (Oh the biomes you'll go), and I'm unable to use buttons made from BYG wood in recipes from create.

Having just fixed this issue myself, this isn't an issue with Create, it's an issue with BYG. Create's cogwheel recipes use the wooden_buttons item tag, however none of BYG's wooden buttons have this tag, even though they should. You can fix it with a crafttweaker script or something similar.