extra_drag_preferred_action
Description:
The unique action on the `current-drop` of the [signal@TabOverview:AdwTabOverview:extra-drag-drop
].
This property should only be used during a [signal@TabOverview:AdwTabOverview:extra-drag-drop
] and is always a subset of what was
originally passed to [method@TabOverview.setup_extra_drop_target].