Stack Exchange network consists of 182 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
At the moment there are three choices in the Closing > Off-Topics > Migration tab.
Shouldn't the other stackexchange websites
http://matheducators.stackexchange.com and https://hsm.stackexchange.com/
be added to the list?