Currently there is no way to tell by looking at volume if it is active or deactive.
This can get quite annoying when testing things.
(Especially when activate and deactivate breaks the volume half the time)
It would be nice if it showed visually maybe like how hp is displayed on the target volume just so its easier to fix and it would be easier to notice bugs.
Having it visible to all players might be desirable, but not in all cases, as i would prefer the active visibility to only be shown to those that can change it. Maybe an Active On/Off toggle in properties, or displayed on Connection Tool instead.
Another option is setting the volumes visual border red.