Doodad Variations

The Art Tools Documentation says, that i need a model for every variation of my doodad.
So now I have inner_wall0.mdx, inner_wall1.mdx, inner_wall2.mdx and inner_wall3.mdx.
I've imported these files and didn't change the import-directory (doesnt seem neccessary)
Then I've created a Custom-Doodad with 4 variations and selected inner_wall0.mdx for Art - Model File.
The problem is, it just doesn't work.
Every variation is now inner_wall0.mdx and the editor doesn't take the other files automatically.
What do I have to do, that my variations work ?