ZEEK STFU is the best free volume shaper available.
STFU is a super quick to use sidechainer that can be automatically sync’d to host BPM or triggered by MIDI notes and it’s always sample accurate. Using MIDI trigger, you can overcome limitations of very many synth volume envelopes for a myriad of purposes.
STFU can also output CV for use with lots of hosts and modular plugins.
And if that isn’t enough, you can set up 2 separate envelopes and crossfade between them for all sorts of cool stuff.