Is it currently possible to access client_metadata (application specific metadata) from a customized hosted login page? I don’t see the information being stored anywhere on the ‘@@config@@’ object, which is where I would expect it.
No, it’s not available in the hosted login page.
client_metadata could i.e. be used to store some kind of client-specific credentials or secret keys to be used i.e. in rules. In any case it’s meant to be used on the server-side only (i.e. in Auth0 rules engine, see example on https://auth0.com/docs/rules/guides/metadata) and should therefore not be exposed to the browser/end user.