This post is just a follow-up to an existing post by @M_Mulder:
I would've replied there but it was closed and I don't see a way to ask for an edit.
I ran into this same issue and while mushing all of your components into index.tsx will work, what I found is that Retool's Custom Components Library doesn't like import *. In my case, anyhow, I was able to work around this bug by changing import * from ... to import { A, B, C } from ....
The tricky part is that both versions compile fine and the Retool tooling will indicate success, but the first version made my component disappear.