I know there is a lot of posts out here describing it. But im having a problem with the following steps. I've looked everywhere but cant find the "Steamcontroller under RL" & choose "Toggle multi button ON"

Go to Rocket league bindings and change the bindings of for this example Powerslide. Leave powerslide as your preferred game pad button. however, change the keyboard binding to ex. F11.

Go to the Steam controller options under RL, choose the button that you also want powerslide in,

choose the "Toggle Multi button ON"

Now, select F11. (make sure you check that the Gamepad button remain on (Green) as that can dissapear if you click something else and ruin your regular RL button.

The steps i followed comes from @Poisonedhero (https://www.reddit.com/r/RocketLeague/comments/7bg7sg/how_to_set_one_action_to_two_buttons_steam/) // ALL CREDIT GOES TO POISONEDHERO!