Remember that those default keybindings have no other effect settings saved. (colors, speed, etc)
To update the effect, get an effect configured the way you like it and copy it.
Paste it into a text document and copy the effect starting with the "E_" text.
Paste that between the > < in the keybinding.xml file as shown in the first keybinding for the O key.
Save and restart xLights.
YOU MUST NOT HAVE xLIGHTS running when you do this as it currently saves keybindings on exit and will overwrite your changes if you're editing with xLights running.
I used numbers for my effects and now have single key morphs for up, down, left, right, etc.