Why are there only two options for the migration target site?

Question

If you vote to close question as off-topic, and then chose 'This question belongs on another site on the Stack Exchange network', you can select a community to which it should be migrated. However, you only have two options, namely this meta community and saound.SE. Why is that?

I'm fairly certain (like, 96.5%) I've seen a search bar on another SE-site where you could search and select any SE-site as the migration target. Does such an option exist? If so, was it disabled on video.SE for some reason? Or is it only available at a higher reputation threshold than the normal moderation tools? I would really like to be able to direct a question that is off-topic here to the appropriate SE-site, which isn't possible in many cases at the moment.

For example, this question is off-topic for video.SE, but is a good fit for webapps.SE:
Does opening a youtube link in incognito count as a view?

Or this question, which might've been a fit for either webapps.SE or Stackoverflow:
Youtube Views and Likes [closed]

Answer 1

Migration targets for a site have to be setup by request and there are a limited number available for each site. There needs to be sufficient quantity of posts that regularly need to be migrated. Stack Exchange staff then setup the link in the background.

Sound Design and Video Production are actually something of a special case as normally migrating to a beta site isn't a public option, however, as the two sites were originally one site, it was allowed.

Moderators have the option to migrate to any site in the network, so you can flag it if you don't see the site you think it belongs on. In this particular case, the question did not seem like a strong enough fit in either of the suggested sites to migrate. (Moderator migration also carries with it a more stringent set of requirements to be a good quality question and a good fit for the site. Just because a site might tolerate a question if it was asked there does not mean it should be migrated.)

The limitation is in place to prevent poor questions (either by quality or by fit) being pushed around the network. Common cases are pushed out to high rep user votes to reduce moderation load, but any movement other than that is handled by mods.