don't check for subsequent indices (n), but for child positions; This way

don't check for subsequent indices (n), but for child positions; This way
it's also possible to enable/disable menu/item entries with higher numbers.
This can be useful for adding entries from other config files (aircraft
specific or local). I'd say aircraft files can use indices starting with
[100] and local files starting with [1000]. Such high number will never
collide with an entry in menubar.xml, even if entries are added/removed
there.