I need your help about how to open MIDI-learn for a parameter in VANGELIS
my Zynthian has touch only interface
Do you have these onscreen buttons? Otherwise do you know how to enter the OPT/ADMIN menu? (I guess touching the title bar)
Then you might try OPT (Chains menu) → the grey top menu entry of the chain you want to learn → MIDI learn → Enter MIDI learn → Move virtual encoder → learn.