Publicado originalmente por Artfunkel:

Fixed in 3.4.1. The Action name will now be used instead of "Legacy Slot".

epic tyty <3

Don't understand this new system that Blender has or why it'll only let me export things as "Legacy Slot".

How do I export the animations that I made?

Well this is embarrassing. It turned out that what I did worked, but I was saving to the wrong DMX.
Thanks anyways.

I don't know why I'm getting this, my weights are mostly only 1s and 0s and I've checked everywhere where they would overlap and didn't find any more than 2 bone influences on a vertex.
I even tried using "Limit Total" and set it to 3, 2 and 1 and that didn't fix the error StudioMDL keeps giving me.