I would love to have plex add an icon next to my synced content, so that when I browse my music library, I can see what is not on my device and add it, instead of having to go back and forth using the server switch button, wondering whether I already synced an album.
+1; highly supported.
Hi jboussard
I don’t know for iPhone, but this feature is already there in Android apps. Once Sync, a little white arrow will appear on the “synchronized” Movie/Music Album/SmartList thumbnails whatever if you are in a library screen, or the PLEX home screen (recently added lists).
Please verify by yourself 
Wishing to all PLEX Folks, an happy new year 2017!
Early 2021 clean-up: implemented
