Draft: drag_overlay: Hide internal GtkRevealer when there are no DnD operations
Before this commit, the GtkRevealer made it impossible to select widgets behind it in the inspector. Now, it is possible by making it visible only when needed.
| Before | After |
|---|---|
| Grabación_de_pantalla_desde_2024-08-07_15-09-59 | Grabación_de_pantalla_desde_2024-08-07_15-10-39 |
Drag and Drop operations still work as expected: