I looked for a way to to this but could not find one.
 
Provide a way to control from a MIDI out (track) any parameter normally controlled by an envelope.
The easiest implementation would probably be a MIDI FX.
Insert the FX into a MIDI track's bin. The MIDI note or velocity events in the track would be available as envelopes which could be used just like a normal envelope.  
 
The ability to export an envelope as a MIDI file and import an envelope from a MIDI file would probably provide the same functionality but not in real-time. Either way, this Envelope to/from file capability should be added.
 
If someone knows how this can be done currently, let me know and I will remove this post.