If Zephyr is integrated with Jira, you can create sub-tasks for your defects. To do that -
1. Select the defect you want to add a sub-task to by ticking the check box next to its ID:
2. Click Create Sub-task above the defect list.
3. In the subsequent window, choose Sub-task as the issue type and click Next:
4. In the next window, fill in the required Summary and Description fields, populate the other fields, if needed, and click Create:
Now if you open this issue in Jira, you will find the created sub-task in it:
See Also
Jira Integration
Creating Defects
Searching for Defects
Editing Defects
Exporting Defects