On a keyboard,
T turn on/off subtitle,
L switch next subtitle,
M show the menu,
I can't remember if those key are mapped on the pad

you have to check the file : recalbox/share/system/.kodi/userdata/keymaps/remote.xml
and
recalbox/share/system/.kodi/userdata/Lircmap.xml

and configure with : http://kodi.wiki/view/keymap

You can also use the android app kore on you smartphone