Volume Button Burst photo mode

I was having problems with the burst function on my iphone, now with the update of the IOS14 they have adjusted the function and returned “half the way” as before, because it is only possible to use the “volume up button” by the camera settings and activating a switch. My suggestion for the next update would be that it was possible to choose which button and which function of each button, not only the volume up button, but the “volume down button” as well. I have underwater photography equipment that doesn't work anymore for that reason.