How does one start playback based on where the cursor is in the MIDI Editor (Ableton Live 10 Suite, Mac)?
ANSWER: In Live 10 there is a "Multi-clip Title Bar and Scrub Area" at the top of the MIDI editor and clicking a location there will play back all parts from that location. It's not as good as what I was looking for, something linking the playback cursor in the Arragement view to where you click in the MIDI editor, but scrub area playback works.