When in JSE or other cases in StackOverflow, I found questions that are off-topic and should be closed because they should be asked in the other site, I am following the flag link and the given explanations, when I am reaching at the point that this question should be asked to that X,Y,Z site... But usually the options there are minimum and usually not the ones I am looking for.
So I am wondering, how does this work and what defines which websites should be available there? And why it's not possible to select from all other SE websites?