How to make error response from outputs at ports 2-3 reader friendly❓

The error displayed by Toast is very JSON looking:
{ "error": { "code": 400, "message": "EMAIL_NOT_FOUND", "errors": [ { "message": "EMAIL_NOT_FOUND", "domain": "global", "reason": "invalid" } ] } }

Any better idea than these failed tests made with LOOKUP? (none of the 'output of another node are accepted in the formula)
LOOKUP(outputs["Sign-in"].resBodyRaw, "message") or
LOOKUP(LOOKUP(outputs["Sign-in"].resBodyRaw, "error"), "message")

It fails because the response body has a schema that the Composer doesn’t know before it gets the response. You can create the schema when you open the logic flow in the editing view and “double-click” the logic flow. And there you can set the outputs. Or you could add the DECODE_JSON() formula around your outputs["Sign-in"].resBodyRaw.

Does not work, returns an empty toast. I tried with single and double quotes too, got nothing.

I don’t understand. You mean edit the http request or toast flow function? There is no such option. How do I do that?