Jira

How to make a subtask to issue ...

https://community.atlassian.com/t5/Jira-questions/How-do-I-remove-a-subtask-from-its-parent-issue/qaq-p/1064107

Timesheet for Jira

https://marketplace.atlassian.com/apps/1220750/clockwork-free-for-jira-time-tracker-and-timesheets?hosting=cloud&tab=overview