@Savage has the right approach, the analog 4 can make an envelope as well as a gate. Also, you can use VCV rack as a way to experiment with modular patching to avoid purchasing extraneous modules.
The image above attempts to show that a gate triggers the envelope and then controls the amplitude on a vca.
On a side note, the optomix works quite well as a VCA if you use the VC input as opposed to the strike input, it just also will filter high frequencies at low volumes. It’s a nice sound, and I don’t think it’s a coincidence that Plaits has a built-in LPG as opposed to a standard VCA.