Envolved with well-marked process with sub-tasks (many sub-tasks) and the time spent for each one, my team had the necessity of some automations to facilitate and speed up the daily work on Jira Cloud Platform.
For this, the principals automations required and created was:
- Create the various sub-tasks always needed for all tasks automatically on create the task card
- Calculate the total time spent on task based on times registered on worklog of it each sub-task
- Calculate the total time spent on task based on times registered on custom fields on own task card
We search a lot but never find a definitive ready solution on official platform or on community for this problem, so I ended up doing and help us a lot !
I hope help you all too! 
Check on: https://github.com/GTessarini/JiraAutomations
