Issue Details:

n the Kanaban backlog, if a story has subtasks, then you can't drag the story onto an epic to add that story to the epic.

After you drag it, it comes up with the message "you can't add sub-tasks to epics" - note that I'm not dragging the subtasks, but the actual story.

Workaround:

The workaround is to drag only the parent Story so that it will work.

e.g.,
In the below example, 'Story 2' has a sub-task and 'Story 3' with two sub-tasks in it.

Click on the greater than symbol against the parent story so that it will display the sub-task in it.

Now, drag only the 'Story 2' to Epic panel so that it will be added to the epic.

Suggestion:

The concern is that most of the normal users are not aware of this workaround and it would be helpful to display the UI error with specific details instead of generic error - "you can't add sub-tasks to epics".