I had started a project with the scenario editor, and I saved it. Now I downloaded the custom supports, and it won't let me use them in my scenario! I'm guessing because I couldn't put them on inventions in the scenario editor because I didn't have them yet. Is there a way I can change this with out starting from scratch?

I think you have to research them

I can't. I didn't have them when I had to set the inventions.

Open your park in the scenario editor, and then set the custom supports to researched, save your park, and re-open it in freeform mode. You should be able to use them now

That worked. Thanks tikitiki.