Mode shifting is like a really quick configuration option to do this stuff. As soon as you start clicking down the touchpad button, it'll work like a mouse, and when you stop clicking the touchpad button, it'll work like a normal gamepad. Otherwise, when the touchpad is NOT clicked, touching the touchpad acts like taking a screenshot, and pulling the trigger sends the W key. So now right pad click changes TWO inputs - it makes the touchpad act like a mouse when the touchpad is clicked, and it makes the trigger act like a mouse click when the touchpad is clicked. You could use Photoshop with a gamepad through Steam Controller API if you wanted to. You can use a controller to control things like Firefox or Windows Explorer. Things like Sim City can be played with the controller. To give you an idea of how deep this is, you can play ancient MS Dos games, like Jill of the Jungle, which have NO controller support at all, just fine using a controller with the Steam API. The end result is universal support for every game, no matter what game you are playing, no matter how they built the game, you can use any controller with it thanks to Steam API support. If you are using some weirdo 3rd party controller that nobody has ever heard of before, the Steam API lets you define the controller in terms of an Xbox Controller so it'll work.
This goes even further for games which have NO controller support at all, because you can use the Steam Input API to make your controller appear to the game as a keyboard and mouse. So if you're playing a game that has no Dual Shock 4 support, the Steam API will make the controller appear like an Xbox controller to the game you're playing, while giving you all sorts of options to remap your controller to any form of input recognized by the game.
RESIDENT EVIL 6 STEAM GAMEPAD PC SOFTWARE
The Steam API is a piece of software built into Steam that makes your controller appear as other forms of input to the game you are playing.