remap ab shutter 3 buttons to record video

I have a lg g5 with the built-in camera app.
I bought a remote shutter (ab shutter 3) which is a remote control (bluetooth based) for the camera which has two buttons: one for android and for iOS (iphone).
Apparently, the “iphone” button also works for androind (I think it is the ‘volume up’ button but i’m not sure).
The shutter works great but the problem is that both buttons take a picture.
What I want is to remap one of the buttons to make video recordings.
I think that this problem is equivalent to remapping the ‘volume up’ button in the built-in camera app to make video recordings instead of taking pictures.
How can I do that?