Steps: Click "flag" for a question. Choose "should be closed", then "off-topic because" and then "This question belongs on another site in the Stack Exchange network". I, at least am then shown two options for "another site": "belongs on electronics.meta... " and "belongs on superuser.com".
But say it belongs, IMO, on neither, or even specifically, on, say, "Signal Processing"? How does one indicate that?