This will have to be scripted.
a simple snip-it in eel. What do you want to do next?
item = GetSelectedMediaItem(proj, 0);
take = GetActiveTake(item);
VolEnv = GetTakeEnvelopeByName(take,"Volume");
*hmmm... only works if the envelope is shown already (I'm assuming you'd want to show it if it's not shown). will have to dig in to check the toggle state of the env.