I’m currently duplicating several tracks with Synplant, where different branches are activated, and I’m adjusting their automation individually.

It would be more convenient if I could control the automation of each branch directly in my DAW (branch volume, on/off).

It's already possible with one instance.

Assuming you use Ableton, if you click on the arrow near the device on/off switch, then click Configure... then click and drag each branche in Synplant UI they'll become automatable individually, either by drawing automations, recording automations, or pointing LFO's to them (wish Synplant had LFO so this ould be saved as presets).