As a generally pleased Vega Pro user, I remain mystified at the lack of clip audio envelopes. I hope my comment about this oversight could be taken as a plea for adding this small feature.
Are you referring to an audio event envelope as opposed to the whole track envelope?
Yes, the audio event. Sorry, I guess "clip" is an outdated term.
I always found clip envelopes handy in Cakewalk/Sonar because they moved, copied, and deleted with the event. Closest Vegas comes to that functionality is the option to Lock Events to Envelopes so that track envelope points above events move with them. Auto-Ripple (ctrl-L) also lets you delete a portion of the timeline or close gaps, while moving affected track envelope points together with markers.
If you want to lower the volume of one event, you can do this. If you want to transition (like fade the level up and down) then you have to use the track envelope.