as suggested by jfroco https://github.com/libretro/px68k-libretro/pull/81
"enable mapping of the select key of the joy1 to one of these keys: XF1, XF2, XF3, XF4, XF5, F1 or F2, configurable via Options
This allows to start this games using select key of the joy1:
Kyuukyoku Tiger (press XF3 to insert coin)
Parodius Da! (press F1 or F2 to start)"
as suggested by jfroco https://github.com/libretro/px68k-libretro/pull/81 "enable mapping of the select key of the joy1 to one of these keys: XF1, XF2, XF3, XF4, XF5, F1 or F2, configurable via Options This allows to start this games using select key of the joy1:
Kyuukyoku Tiger (press XF3 to insert coin) Parodius Da! (press F1 or F2 to start)"
modified to match current code base
also assigns keyboard keys OPT1 and OPT2
details : https://github.com/libretro/px68k-libretro/issues/89 @twinaphex