For config-extensions.def:
  What do you think about moving all shortcuts to config-keys and then
always use the name of the shorcut in config-extensions instead of the
shorcut ?

For config-main.def:
  For the [Keys] section I believe it would be better to rename the
"default" option to "custom". If custom is true, then idle uses the key
set defined by the name option, otherwise it uses the one that fits
better the platform. If the user changes the key set that supposedly
fits better his platform through the "Configure IDLE" dialog then we set
custom to True (independently of this new key set being a custom one or
a default one but that is not the default for his platform) and set the
name option to the name of the key set. Any thoughts ?