I'm not positive, but I believe those spread springs hold the three shifting inserts in place when they are installed on the 3rd/4th synchronizer hub. There are 2 inserts placed on the left side of the hub (if looking at the pic), and the third on the other side of that same hub. If you look at the pic, the are 3 gaps within the teeth of the hub. That's where they are placed. Underneath the spread spring "arrow", they show a shifting insert below it. That's what goes in those slots.
I hope this helps.......and in my opinion, if it's in the diagram, it should be installed, especially on the tranny.