Speed up button on switch 1 (using handheld mode)

Hello,

I have a question regarding how to activate the speed up button when using switch 1 in handheld mode. 

On the bottom right corner, it suggests that the button would be using the "-" button on my right joycon, but pressing or holding that button actually does nothing to me? Am I using the right button? In the game help menu, this function is straight up not being mentioned... Despite every other buttons are mentioned. 

Obviously, tapping on the touchscreen directly works, but if I am using a controller to play I don't want to let go of the controller just to adjust the speed? 

Is this a bug or am I doing something wrong?