Pull the back button (from where it attaches to the controller) towards the top of the controller, and lift it from the slot.
How to change the trigger length/stop of the L2/R2 buttons
You can set how far the L2 and R2 buttons go when you press them (stroke). Simply move the L2 and R2 stop sliders on the back of your controller.
Starting from the top, you can set the stroke to long stroke, medium stroke, and short stroke.
If you set the stop sliders to medium or shallow strokes, the trigger effect function doesn't work.
How to set DualSense Edge wireless controller profiles and settings
You can also personalize your controller stick sensitivity, deadzones, button assignments, vibration intensity, and trigger effect intensity by creating custom profiles on your PS5 console.