HOW DO WE ENTER ARRAY IN FIRETABLE?

The closest I can find it's Multi-select, which only takes strings of predefined options. It hints me that the user can enter custom values, but so far, I DON'T how to turn that option on.

How about array of integers?

Alternatively, I try JSON, but it doesn't seem like to allow array at the top level even when I turn on "Set as an Array" IN THE COLUMN