Keith (and others)
https://github.com/neilkplugins/WLED-indigo-plugin/releases/tag/1.0.2-beta is a beta version including the sync functionality.
It implements the API calls correctly, and for the Mobile UI it has a clear action to toggle the "Sync Lights" option in the Mobile WLED UI.
The control of "broadcasting" UDP states is a little trickier. It varies between the Classic and Mobile UI's in WLED, and more granular control of the sync functionality comes from the WLED sync settings. I haven't quite figured out what and how these all interact. That said.
- If you set one WLED to "Send Notification on Direct Change" in the Sync settings, other WLEDS that listen on the same UDP port will sync if you use the action "Set UDP Synchronise Mode" to true. The "syncToBroadcastUDP" device state will also reflect this and the "Sync Lights" option in the Mobile UI
If you use the Classic UI, it has a different approach, with Sync mode and broadcast mode represented by two arrows. The two actions I created toggle those arrows, but I don't quite get the expected behaviours, and it is not clear the order of precedence between the API, UI modes (Classic and Mobile) and the Sync Settings themselves.
The bottom line is that if you dedicate one WLED as a master, you can then toggle the others to follow it or to operate separately. It may not be a big deal (and indeed confusing) to have multiple WLEDS broadcasting and acting as a master (in which case I will re-label the broadcast actions).
I will do more experimentation and documentation..
Apologies, you may need to open and save the device configuration again if you get errors when upgrading from 1.0.1, will also look to implement Dave's guidance to handle this more elegantly for the formal release.