Years ago I made a custom layout and didn't know what I was doing, so somehow it's in My Layers as "User" rather than "Theme." It works fine and I've been able to tweak it and all. But now I am trying to learn how to do it right, and I've created a new Theme to practice with.
My question is: I can see where to switch to the new Theme to test it out. But how do I switch back to my working custom layout, which is User, whatever that means? What does it mean, anyway? Can I convert it into a Theme?