While docked, hold ctrl while dragging the window tab to put it in a different spot. Actually maybe it changed, but seems like you don't even need to hold ctrl anymore... But yea, you can put it on the left.
Yeah, but that will only work, if you have the MIDI Editor docked. And it will give you the same docked items as in the arrangement. I would like to have a dedicated MIDI editor docker.
Not sure what you mean. There isn't just one dock area. You can have multiple or single windows docked in multiple places. If you don't dock anything else on the left then it's exclusively for the ME.