Playback speed - map remote

Hi,
Does anyone know how i can map playback speed in-/decrease on Nvidia Shield to certain remote key. Maybe there is a keyboard shortcut that i then can map?
Thanks

Playback speed on the smart tv apps requires you to go though a bunch of steps for every single play. Regardless if you are playing a collection, tv show or a playlist.
I want to add a default speed to my account.
At this point I want to binge some 20 min shows at 2x speed yet that requires me to fiddle around finding the remote, then changing the speed for every single episode or even movie. Its annoying that I might as well go back to using VLC player where I can add all the shows to a playlist and set a default speed and sound level and play away.
I was unaware that you can map keys in Vvidia Sheild. I wish you could do that with Roku.