I have been on the hunt for what exact shortcut the controller hides from us. But there is a steam menu (controllers, advance, show more, at the button) that shows them!
Quickly want to change your volume? Try steam key + left joystick!
Sadly you can not change anything here, altought the menu shows you you can, nothing will be saved after you leave a menu. (I'm not a fan to put the left mouse button on the right button)
A few of them I manually found before written out, also for the people without images:
hold A + R1 + Steam
To use Puck wireless mode right
hold A + L1 + Steam
Start Puck wireless mode left
hold B + R1 + Steam Start Bluetooth mode
When on (solid white)
Steam+Y Turn off quickly
Hol steam (10s) Turn off
Steam + left joystick up/down Change volume level
R4 + R5 + L4 + L5 + Steam Backpack mode (ignore buttons until this combo is used again or USB)
Steam + Right trackpad/joystick Mouse movement
Steam + X On screen keyboard
Steam + R1 Take screenshot
Steam + Menu ALT+TAB
Steam + D-pad right Enter key
Has anyone tried the steam controller on an Nvidia shield, even via steam streaming? Very curious to know if that works alright...
The right trackpad will show a mouse on the screen and clicking the pad will function as selecting what you are hovering over. Left trackpad can scroll. This is with the puck plugged into the shield. I can do some more testing in a few hours.