Add “import System.Collections.Generic;” in your script. You can use List in JS without that line, but it won’t show in the inspector, and other things from Generic don’t work either (unless you include the full namespace of course), which is kind of weird. I think they should include the namespace automatically, like with UnityEngine and System.Collections, or else List shouldn’t work at all. Having only List (mostly) work without importing the namespace is kind of confusing.