Here are some of it’s applications:

FISH GORGE – bait is placed on the fish gorge with the purpose that the fish will swallow the bait and gorge in whole that in turn will twist within the fishes gullet or mouth allowing the fish to be caught and retrieved.
TRAP AND DEADFALL TRIGGER – Traps and deadfalls use stored energy from a bent sapling or from elevated dead weight. The toggle enables a delicate trigger to be placed in such a way as to release these devices to snare or crush the intended small game animal.
TARPS / CLOTHING – A toggle can be passed through a grommit or loop and when turned 90 degrees and will hold fast a tarp or join the seam of clothing.
HAMMOCK SUSPENSION – Hammock enthusiasts have found that a quick way to attach tree straps to their hammock lines is by using a toggle. In lieu of an actual toggle a small bar is used as a marlin spike that in turn performs as a toggle for connection.
SURVIVAL WRIST BAND – A simple attachment for the popular paracord wrist band is a small ferro rod that can be used to start fires when needed. The ferro rod is the toggle that is placed through it’s corresponding loop.

You can see from these examples how effective toggles can be which is why this is such a valued tool throughout history. You may find other applications but it’s a good tool in your survival knowledge base that could make a huge difference in a survival situation.