Currently in Jira Cloud, subtasks cannot be independently assigned to sprints — they always inherit the sprint from their parent issue. When a user attempts to drag a subtask into a sprint from the backlog, they receive the error: "Subtasks can't be moved from their parent on the backlog."

Subtasks should be able to have their own sprint fields independent of their parent.

Workaround:

Use an Epic as the parent instead of a Task

If Task T1 represents a larger piece of work spanning multiple sprints, you can convert it to an Epic and create the 7 items as Stories or Tasks under it. Unlike subtasks, child issues of an Epic can be independently assigned to different sprints:

• Sprint 1: Story-1, Story-2, Story-3 (under Epic T1)

• Sprint 2: Story-4, Story-5, Story-6, Story-7 (under Epic T1)