La config clavier de recalbox ne gère que 2 boutons + directions + start +select et page up et down cf. ci après le contenu de /recalbox/share/system/.emulationstation/es_input.cfg
<inputConfig type="keyboard" deviceName="Keyboard" deviceGUID="-1">
<input name="a" type="key" id="115" value="1" />
<input name="b" type="key" id="97" value="1" />
<input name="down" type="key" id="1073741905" value="1" />
<input name="left" type="key" id="1073741904" value="1" />
<input name="pagedown" type="key" id="1073741902" value="1" />
<input name="pageup" type="key" id="1073741899" value="1" />
<input name="right" type="key" id="1073741903" value="1" />
<input name="select" type="key" id="32" value="1" />
<input name="start" type="key" id="13" value="1" />
<input name="up" type="key" id="1073741906" value="1" />
</inputConfig>
après je sais pas si c'est judicieux de modifier le fichier !