No can do. S1 is based on a one screen environment (obviously not one monitor though). Mixer and editor can be un-docked, and relocated, but you get one and one only.

damn that sucks, i would like to have different midi parts editor windows opened when writing music.

For editing instruments, you can fool around with selecting several events, then double click on one of them and have a multi view of those events. To the left in the edit screen, expand to select those tracks. Or if the notes are not completely from start to end on top of one another, selecting that note will select that instruments set of notes. I was just doing this last night, and it worked just fine for multi event note editing. If the events are not in the same region, use the arrangement view timeline to get to the desired location. The edit view of that event will appear, ready for editing there.

Explore that, and see if it helps with your workflow.