Enable Show docstring in the menu or the config. Then:
>>> def foo(x: int) -> str:
... """Lorem ipsum."""
... pass
>>> foo(
──────────────────────
foo(x: int)
Lorem ipsum.
The docstring window shows the type annotations of parameters but it doesn't show the return type annotation in the signature.
I find this to be unexpected because the Python builtin help does of course show the full signature for help(foo).