It seems that simply selecting a track, then clicking on
Views > Step Sequencer will open a step sequencer for any track, or reopen an existing Step Sequencer for that track if work in progress exists.
Alternatively, double-clicking on the clip in the track will reopen an existing step sequencer view for that clip.
This makes more sense than a multi-out drum example, if you are trying to use more than one independent soft synth in their own instrument tracks.