TLDR: Bind Alt+F1 to xfce4-popup-whiskermenu, apt install xcape, add app to startup xcape -e ‘Super_L=Alt_L|F1’
On most desktop environments, you hit the super key (or windows key) on your keyboard and the applications menu appears where you can type stuff. On XFCE, this is not the case. You can set the super key to open xfce4-popup-whiskermenu but then you can’t use the super key as a modifier for other commands like super-d for show desktop or super-e for your file manager.