As for the sub-tasks - any issue placed in "Scheduled Issues" table (also with "inactive" status), can be managed with sub-task linking. To do do,
Subtasks in Cloud
To manage subtasks simply click "Add subtasks" button placed next to the name of SI.
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A new prompt with all necessary information will be presented:
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Any created sub-task can be quickly replicated or removed - when you hover a mouse cursor over any of existing sub-tasks(1↖), two more options are to appear at the same time - clone and delete. Move cursor horizontally to the right (stay on the same line as a sub-task is placed) to choose a desired option.
Subtasks in Server, Data Center
Subtasks management in Server and Data Center is easy. You can add them to any Scheduled Issue in Jira in two ways. Go to Scheduled Issue details page and click on the “+Add” button (1) or Add Sub-Task in More actions (2).
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Both operations result in displaying the following prompt on your screen. You can set here all details of Subtask. Remember, that the fields that will be displayed depend on the settings in your Jira project.
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Fill all information that are important to you and create a subtask using “Add” (1) button.
In Scheduled Issue details page you should see that Subtask has been created (1). If you want to do some changes you can click on the edit button (2). Then you should see similar prompt as during creation. Confirm changes clicking on “Save” button.
Subtask can be also removed easily using the delete button (4) or trash icon (3).
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