PlantUML Activity diagram special Box Layout Output is needed - layout

Question

I have a problem and tried to solve it for the last 2 Days.
I want to design an activity diagram/flow chart like this:
Step1
Step2
Step3 --------->Output of Step 3
Step4
I can't draw/program an arrow which starts directly out of the box "Step3" and the Box "Output of Step 3" too without any layout problems.
My current code:
#startuml Test1
title Flowchart
|System 1|
start
:Step1;
:Step2;
split
:Step3;
|System 2|
split again
:Output of Step3;
detach
|System 1|
end split
:Step 4;
stop
#enduml

Answer 1

Activity Diagrams in UML have certain rules. Using split is probably a bad idea, as it's intended for the SDL aspect of PlantUML.
Perhaps you can try with fork if you want to show the output in a separate swimlane:
#startuml Test1
title Flowchart
|System 1|
start
:Step1;
:Step2;
:Step3;
fork
:Step 4;
|System 2|
fork again
:Output of Step3]
stop
|System 1|
end fork
stop
#enduml
I put a stop at the end of the output (which is now an object using the ] ending) to prevent the line rejoining the flow in System 1.
Another alternative is to use the legacy syntax for Activity diagrams, which doesn't allow for swimlanes, but can do partitions.
#startuml Test2
title Flowchart
partition "System 1" {
(*) --> "Step 1"
--> "Step 2"
--> "Step 3"
--> "Step 4"
--> (*)
}
partition "System 2" {
"Step 3" -> "<< object >>\nOutput of Step 3"
}
#enduml
In the legacy syntax for Activity Diagrams, it's not possible (as far as I know) to make an "object" (rectangle) shape.