The filter function to search playlists will be coming back in a future update;
The devices section will also be coming back in a future update.
In the meantime:
You won't be able to see an indication in the desktop client that the device is paired with the desktop client. But as long as they both are on the same WiFi network you should be able to trigger the local files sync by toggling the offline toggle on the playlist on your phone. Just make sure all your local files are in the playlist you switch to offline in the desktop app.