Remove and re-insert female threaded insert?
Cut the rod to the desired length. Then get a rotary tool like a Dremel with a cutoff disk. Cut the tubing that holds the insert lengthwise down to the surface of the insert. Make three or four cuts. Then pry the tubing apart with a slotted screwdriver, freeing up the insert. Slightly chamfer the inside edge of the shortened length of tubing and tap/pound the insert into the tubing.