This question already has an answer here:
Specifically, when reviewing "close votes", I like that the "close for being off-topic" dialog suggests sites for migration, but some questions deserve to be migrated to Apple.SE and that is not an option in the dialog. How can I suggest these question be migrated to Apple.SE? (You may feel that this specific question was appropriately migrated to SuperUser.com but this is just one of several examples I've seen where I would vote to migrate to Apple.SE.)
It is not a good workflow for reviewers to have to step out of the "close votes" process to flag for moderator attention and even if it were it runs the substantial risk (as in the question cited) that the vote will be finalized to close and migrate to another site before the moderators even get to look at it.