I use to be able to do it, but somehow the latest patch ruins it. Whenever I make an armature that’s symmetrical like for a person, I make all of the bones for only one side. Then, after I’m done making all of the bones for one side, I set the pivot to the center of the mesh or center of the origin and then I simply copy and scale the copies across the x axis by a factor of -1. This use to work and there’s tons of tutorials showing it works, but not all of a sudden for no reason, it doesn’t work.
Can’t try it right now but you should probably report it as a bug if you’re sure about it.
The current tool to perform that function is Armature->Symmeterize. Select the bones you want to mirror. Then run the tool. It will make a mirrored copy, and automatically rename the .L/.R suffix.
EDIT: And actually scaling the bone does now preserve the bone roll. Symmeterize flips the bone roll as is expected.
I knew it was too good to be true. I tried it and I’m not joking, it LITERALLY does absolutely nothing.
The bones being symmeterized have to have proper .L/.R names.
Oh alright then thanks!