Board Thread:Support Requests - Getting Technical/@comment-10637-20170728213209/@comment-27345308-20170728221504

Not all do. You can use ImportJS to bypass JS review, so you can use ImportJS when you want to import a script from local wiki or Dev Wiki. In any other case you would have to click "Submit for review" button in the sidebar module to submit a MediaWiki page ending with .js for review for other people to be able to import it. There's information about that on Help:JavaScript review process.