Improve sort dialog UX: Drag & drop ordering #606
Description
The current arrow-based ordering is inconvenient when there are many sites. To improve the UX, the sort dialog should support drag & drop reordering. Drag & drop support in the treeview is currently out of scope / not planned.
Acceptance Criteria:
- Sort dialog supports drag & drop for ordering sites
- Arrow-based ordering can remain as fallback (optional)
- No drag & drop implementation in treeview