Features used to implement the example

• Transition issues

Example: Moving story to "Ready for QA" once all its sub-tasks are in "Ready for QA" status (Transition issues)

When all sub-tasks of a story are moved to "Ready for QA", the story should move from "In Progress" to "Ready for QA". 
Insert Transition issues post-function into transition from "In Progress" to "Ready for QA" in sub-task's workflow:

Text to be parsed is: count(siblingSubtasks()) = count(filterByStatus(siblingSubtasks(), "Ready for QA"))

That boolean expression checks that all the sub-tasks are already at "Ready for QA" status. It is also possible to check the sub-tasks against more status, e.g. "QA Accepted" and "Done". In this case the following expression can be used:

count(siblingSubtasks()) = count(filterByStatus(siblingSubtasks(), "Ready for QA, QA Accepted, Done"))