Hm...
I could add an additional command like "Open in new (pinned) tab" to the note list context menu. This command you can assign keyboard shortcuts then. But honestly I have no idea if it is possible to assign mouse buttons also.
Maybe someone else here knows if this would be possible. I would also be very interested in this, because I would like to assign the history forward and backward commands to mouse buttons.
Regarding your second request... I'm not sure if this is possible. I will check if it is possible to overwrite the click events for the rendered markdown view.