This is a MusicBee plugin to synchronise local MusicBee playlists to Spotify, and vice versa. Syncing with Google Play Music was removed after Google deprecated the service.
Download at https://getmusicbee.com/addons/plugins/306/musicbeesynctoservice/ (or check latest releases)
Install by extracting and putting contents in your music bee plugin directory
Once installed, in the header bar at the top, go to "Tools" then "Music Bee Sync To Service", and a window like below should pop up
