I think similar question is asked in past but I assume that this is not working as it should.
"Charlie -down-> Dennis" result is that Dennis is right of Charlie.
@startuml
package Bob{
class x
}
package Alice{
class a
}
package Charlie{
package kids {
class c
class d
class l1
class l2
class l3
}
package friends {
class h
class i
class k1
class k2
class k3
}
}
package Dennis{
package kids {
class g
class g2
class g3
}
}
Bob -down-> Alice : down
Alice -down-> Charlie : down
Charlie -down-> Dennis : This should go down
@enduml
Commenting (removing) classes l1, l2, l3 and k1, k2, k3 will make those packages within Charlie as one "row" and that will move Dennis below Charlie. Assuming Dennis should be always below Charlie because "Dennis -down-> Charlie".
br,
Hannu