There is no skin manager anymore. I'm not sure exactly when it was deprecated, but it was probably at least five years ago.
As you noted, you can access and switch skins via the view menu - that is effectively the skin manager now. It shows all the skins that come with MC by default, as well as any other skins you may have downloaded from the plug-ins page.
At the top of the menu where all the skins are listed is an option to launch a dialog called Skin Effects. Here, you can adjust contrast/brightness, and swap the default skin colors to give a different look, along with a few other options.
