Is it possible to set Bamboo variables in one stage ( via custom task) and retrieve it in a different stage

Question

Use case
A task may define some *custom build variable* that would need to later be retrieved in subsequent tasks. 
The current mechanism to handle this is to share artifacts between the tasks - the problem with this approach is that the "native" bamboo tasks, such as the ant task could not access this "custom build variables"; we would need to write a wrapper script that parses the artifact then invoked the ant command. Furthermore, using artifacts requires to add extra logic in every task to read/write to the artifact.

Is it possible to set a bamboo build variable ( attach it to the plan, see code below) and access it in later stages - without going through artifacts?

Tested case
I created custom build variables using the variableDefinitionManager

VariableDefinition vd = new VariableDefinitionImpl();
vd.setPlan(plan);
vd.setVariableType(VariableType.PLAN);
vd.setKey(k);
vd.setValue(v);
variableDefinitions.add( vd );
 variableDefinitionManager.saveVariableDefinitions(variableDefinitions);

What currently works:

* Pass variables between tasks

Plan
      Stage 1
          Job1
              task 1A: set_plan_variable myVar
              task 1B : print_variable myVar

What does not work:
* Pass variables between a jobs (expected not to work since jobs can be concurrent)

* Pass variables between a stages

Plan
      Stage 1
          Job1
              task 1A: set_plan_variable myVar
      Stage 2:
          Job1
              task 2A : print_variable myVar

Note

I opened https://jira.atlassian.com/browse/BAM-10899 to request the feature, but if someone has a magic trick to share, please do !

Przemek Bruski · Accepted Answer

I think the only way is to have a finalising task that puts all variables into a file defined as an artifact and a task that fetches them from that file in another stage/Job.

As you've mentioned, by design, you won't be able to do that between Jobs in the same Stage. That's why we've introduced Stages in the first place - to serialise Jobs and allow them to pass information between one another.