by Michael Bech Hansen » Thu Jun 09, 2016 7:12 pm
This old post has some scripts that is intended to do what you want:
viewtopic.php?f=15&t=10907&hilit=musicFolderSettings.view%3FscanNowHaven't tried it myself, but had it bookmarked for when I would need it

Michael.
Developer of play:Sub for iOS.
https://geo.itunes.apple.com/us/app/play-sub-subsonic-music-streamer/id955329386?mt=8