Hi Gerd,
I think admin_level9 must be placed before admin_level9 for Belgium:
mkgmap:country=BEL & mkgmap:city!=* & mkgmap:admin_level9=* { set mkgmap:city='${mkgmap:admin_level9}' }

It makes no sense to have a specific rule
mkgmap:country=BEL & mkgmap:city!=* & mkgmap:admin_level8=* { set mkgmap:city='${mkgmap:admin_level8}' }
when the next possible match is the general rule
mkgmap:city!=* & mkgmap:admin_level8=* { set mkgmap:city='${mkgmap:admin_level8}' }

Or is this meant as some kind of documentation (meaning we have verified these rules for Belgium) ?

Gerd