Finding the next subtask assignee, and update the parent Jira

[James]

In each parent Jira, there can be 5 to 10 subtasks. Typically the subtasks are added when the parent Jira is created. However, it is possible that additional subtasks are created on the fly and the order of the subtask may be changed. For example:

Initially,

Parent Jira-001

> Subtask Jira-002 with status To Do

> Subtask Jira-003 with status To Do

> Subtask Jira-004 with status To Do

Later, a new Subtask is added and it is re-order 

Parent Jira-001

> Subtask Jira-002 with status To Do

> Subtask Jira-005 with status To Do

> Subtask Jira-003 with status To Do

> Subtask Jira-004 with status To Do

When Sub-task Jira-002 transition to Done, I would like to have an Automation that will be trigger in which it is able to identify that the next Subtask is Jira-005. It looks at Subtask Jira-005 Assignee and then updates the Parent Jira-001 Assignee to the same as that of the Subtask Jira-005 Assignee.

Initially, I used Jira Automation to create the Sub-task Jira-002 to Jira-004 and placed labels within each of them. So I was able to identify correctly the next Sub-task. But this fails when a new Sub-task is added manually and had been re-order.

Appreciate any advise, help. Thanks.