OK. I’m no expert on the details of this, but I think the Iconica Sketch legato patch is monophonic, so will not play chords.
It’s true that Iconica Sketch’s string legato techniques are monophonic and cannot play chords, but you should nevertheless find the sounds are sustained because even though Dorico will not use the sustain technique, it will overlap the notes.
Oh, OK I understand now about it being monophonic. That must be why it is sustaining the notes through the “sustain vibrato“ technique and not the “slur“ technique. I appreciate very much the feedback. Thank you so much everyone for explaining this to me. You’ve all been very helpful!