Hi @Banstinct
You have a parent execution (main process instance) & a child execution for each parallel sequence flow. The variables you see are defined on the main process instance scope.
You could define variables on child execution scope or even on task scope as each child execution could contain many tasks
Below link describes “Variable Scopes and Variable Visibility”
https://docs.camunda.org/manual/7.5/user-guide/process-engine/variables/#variable-scopes-and-variable-visibility
To define or set variables on different scopes you could use “Execution Listener”
https://docs.camunda.org/manual/7.5/user-guide/process-engine/delegation-code/#execution-listener