A demo plantuml code is here
@startuml demo
package group1 {
package group12 {
component A
component B
A --> B
}
}
package groupA {
package groupAA
}
group1 --> groupA
@enduml
Actually, groupA is to the right of group1, but because gorupA is smaller than group1, its position is lower than group1. The arrow starts from the right edge of group1 and points diagonally downward to groupA.
But what I want is that gorupA is completely below group1. Then the arrow from group1->groupA should start from the bottom edge of group1 and point vertically downward to the upper edge of groupA.