So earlier today I was curious if custom objects will work with the new editor beta.
It is a bit annoying to do as currently you can add all the custom objects you want into the editors media folder, however when publishing the mod it doesnt automatically add the files to the _mod folder. All assets used will have to be manually entered into the _mod folder. After that when you publish it should send the additional assets to your workshop map.
My quick little test using the concrete lane dividers and a custom overlay found in the Russian .zip of a bunch of great additional assets.