Holding it down is akin to holding shift on a keyboard, with customizable key assignments for every button when it's held down. (digitaltrends.com)
Concerning key assignment I can already reveal something, in the Farming Simulator 19 you will be able to search / find shortcuts during the game. (farmingsimulator2019mods.com)
However, that's not an issue as you can customise the buttons from the menu in a very quick and easy key assignment wizard, of sorts. (16bitdad.com)