Drag top-level actions to subactions in Table View

Dragging an action in Table View to an action with existing subactions makes the dragged action a subaction; however, this was previously not possible for top-level actions.

Now, users can drag an action over a top-level action in Table View to convert it to a subaction of that action (similar to Gantt view). This speeds up subaction creation by removing the previous back-and-forth process.

Thank you to Albert at Tabush for requesting this feature!