I think that in the music editor you can click 0(red) to show automations, then press the three little buttons 1(red) to load the automation selection dialog, then press 2(red) Midi Controllers, add the sustain 3(red) to the left hand panel and it will appear at the end of the list when you close 4(red). select the Sustain at the end to show the automation grid for it and then click a few points on the line and drag the mid point between them up MIDI CC value 0 or 127. (on off)... see graphic from S1v5.1 on MAC
