It might be easier if you loosen the lower left heatshield, slide it down slightly, and remove the heatshield just between it and the rear cylinder exhaust port. That will give you the necessary access to the rear TORCA clamp. The clamp is a special one, with a small relieved place in it, to accept the tab from the bracket tab. Catch the broken tab when it comes free (you don't want it bouncing around the top of the starter).
When putting it all back together, do not tighten the keps nut, until you have made sure that the bracket tab is correctly placed flat against the starter mount plate, as well as lined up right up against the rear header, slipped under the relief in the TORCA clamp. Once in the right position, gently tighten the keps nut, just enough to keep it properly positioned, then tighten the TORCA clamp to spec (pretty significant torque, and use a torque wrench). Then tighten the keps nut to spec.
Replace the upper heatshield and tighten just enough for position verification, and slide the lower heatshield up to where its lip slides just under the upper heatshield (as indicated by the relief in the upper heatshield). Tighten just enough for position verification. Slightly loosen and reposition the 2 shields till you find the natural bend matching to the pipes, and tighten them both down.
Note: Don't ride your scoot much at all, until you get that bracket tab properly remounted. The increased vibration will increase the likelyhood of a cracked rear headpipe, significantly. In fact, if it were me, I would remove the heatshields to expose the entire rear headpipe, and check for cracks, if for no other reason than for peace of mind, as long as you are in there. The likely crack points are right behind the rear exhaust port, at the top, and right behind the 'Y' where the rear and front exhaust flows meet, at the bottom of the right side.
Also, wear eye protection while tightening the rear TORCA clamp. This one has gotten quite hot, it requires quite a bit of torque (per spec), and HD advises these to be single use. I don't know why the single use, except that they likely stretch and shape a bit. My point is, if the clamp breaks while torquing, you do not want naked eyes in the area, in case pieces fly.
Enjoy,
Rich P