basedpyright (I tested in Zed) supports "Go to Definition" (cmd-click or F12) for argument names in a function call.

In ty, this is currently a no-op, so you have to use "Go to Definition" on the function, and then find the parameter in its type signature.

Supporting argument names is useful for this pattern, which is used in types-boto3:

class BarTypeDef(TypedDict):
    thing: str


def foo(**kwargs: Unpack[BarTypeDef]) -> None:
    pass


foo(thing="abcd")
#   ^^^^^ cmd-click here

In basedpyright, "Go to Definition" on thing takes you to its definition in BarTypeDef.