[PMX Basic] Merging material layers

The result of mocking with unknown buttons. I hope this actually helps someone.

NOTE: Older PMD versions (thus the English translation) use a different method. ASK ME if you want me to make a tutorial for that too.

~Mayuen told me about a glitch where merging too many layers could cause the model look weird. To prevent this, just undo the step, make the model update itself (change layer order or update textures) and merge the layers one by one.
Thanks for the info.