At some point I did a prototype of “tuple completion”, basically you would write the arguments of a method in parenthesis (e.g. (x, 1) where x is a Set) and on tab it would show you all the methods with that type signature, with (x,...) being equivalent to methodswith. Completion would then add the method name in front of the tuple, making it a valid function call.
I didn’t find it that useful though (it was a bit buggy admittedly). But since InteractiveCodeSearch seems to provide everything you would need to do that kind of search it wouldn’t be very hard to implement it again in an editor.
You could have a lighter syntax, e.g x) alone would trigger methodswith, like f( triggers methods.