unsynced. Prevents the event from being passed to synced event clients (such as synced LuaRules). This is fine.
control. Apparently this means the event returns something to affect further logic flow but I don't think the bit actually does anything. Check if it can be removed, otherwise document what happens if the bit is set incorrectly.
managed. Apparently events without this bit are not handled by the event handler, so you have to keep track of relevant clients yourself and call them manually, which goes against the whole point of an event handler. If an event is truly unique to one client then it should just be a regular interface function for that client and not an event. Otherwise all those events could become managed since any clients that aren't interested in the event just won't register a callback.
Events are listed here https://github.com/beyond-all-reason/spring/blob/BAR105/rts/System/Events.def
They have 3 bits: