<p>What about this possibility? You could leave a comment about the scope of topics on this site, mention your suggested destination and then <em>suggest that the OP flag it to migrate rather than repost</em> (whether you also flag it yourself is up to you) .</p>

<p>However, it's a good idea before suggesting a post belongs on another SE site to make sure it fits with the on-topic page for that site (for example, if it's a post about an error message, it's actually off-topic on SO unless the post satisfies several conditions). Once you're familiar with the requirements for the destination site, you don't need to keep re-checking, but many flags to migrate don't go through because the post actually doesn't meet the requirements of the destination. (Sometimes the post can be edited to meet the requirements and then migrate.)</p>
