L+A. But why don't you just edit the Global.ini, so you won't have to always perform a hotkey press to flip the screens?
This is what you want to look for in the Global.ini(not too far down):
; 1.2 FileSelectSubScreen = [0|1] (Default = 1)
; Defines which screen is used to display FileBrowser.
; 0 = touchscreen (lower screen)
; 1 = normal screen (upper screen)
; ƒtƒ@ƒCƒ‹ƒŠƒXƒgƒEƒBƒ“ƒhƒE‚ð•\Ž¦‚·‚éƒpƒlƒ‹‚ðƒƒCƒ“‚ƃTƒu‚©‚ç‘I‘ð‚µ‚Ü‚·B
; 0=ƒ^ƒbƒ`ƒpƒlƒ‹(‰º‰æ–Ê), 1=’Êí‰æ–Ê(ã‰æ–Ê)
FileSelectSubScreen=1
Just turn FileSelectSubScreen=1, to FileSelectSubScreen=0, and you won't have to perform the button press anymore.