I'm sorry this has been such a pain to figure out. There isn't a keyboard command, but a single tap is all that is normally required. Do you have a mouse connected? I want to make sure you are actually using your finger and not a mouse. If you are using a mouse, you would need to go to Settings->Touch & Pedal Settings and uncheck the "Enable USB Mouse Processing". Then mouse clicks would act identically to finger taps.
Mike
Mike