关于工作流多实例子流程out参数不起作用的解释

Hi Nico...

Based on camunda documentation
(https://docs.camunda.org/manual/7.4/user-guide/process-engine/variables/#multi-instance-io-mapping)

Only Input mappings is supported for MULTI-INSTANCE CONSTRUCTS

NO OUTPUT MAPPING FOR MULTI-INSTANCE CONSTRUCTS
The engine does not support output mappings for multi-instance constructs. Every instance of the output mapping would overwrite the variables set by the previous instances and the final variable state would become hard to predict.

But as Christian said you can access parent process variables.
See below link
https://docs.camunda.org/manual/7.4/user-guide/process-engine/variables/#variable-scopes-and-variable-visibility