I'm having the very same problem.
And have had 0 success in finding an answer to it.
This is normally cause by the skin title and skin file name being different and the skin file name you want being present in the project. What I'd do is save your skin as another name, import it into your project, delete all references to the old skin names and finally rename the skin to the name you want.
The RoboColum(n) @robocolumn Colum McAndrew
Excellent! Thanks that worked perfectly. I can now see the custom skin in the list of skins.
Couldn't get this to work. At what point should the skin display in the list? I renamed it and imported. It didn't appear on the list.
Although it bugs me that the skin isn't available from the Project tab, all I really want to do is edit it.