Hello D.,
A possible workaround will be to use empty map and then a normal arrow outside the map definition;
Here is an example:
@startuml
package foo {
object baz
}
package oink {
map a {
b *-> foo.baz
c =>
}
}
a::c --> foo
@enduml
[See on PlantUML online server]
If that can help,
Regards,
Th.