Our skills database shows it as one of:

1. 75751
2. 75752
3. 76667
4. 78835

This is one I don't have in my spreadsheet yet because I don't have a set handy.

Best way to get those ids would be to turn on all the debug options in Srendarr, grab a buddy with a target dummy and have them cast a synergy then use it and see the resulting ids.

The "buff timers" addon will also show active auras on you or your target if you turn on its debug option (/buti d). Its possible the debuff doesn't actually have an aura to display, but it likely does since even dummy timers for quests in TG and DB do.

If you need any help determining the behaviors of the ids let me know, I've been slowly logging all ids in the game and keeping track of issues and inconsistencies so wouldn't mind adding that stuff to the spreadsheet!

Yeah those are just base game icons. I'll pick through those id's you screenshotted when I get home and see if I can find anything.