Category selection
1. **Click the category selector**
2. **Expand the category tree**: View all categories
3. **Select category**: Click to select the target category
4. **Multiple selection support**: Multiple categories can be selected
5. **Search category**: Enter keywords to search for categories
Category management
- **Tree structure**: Support multi-level category display
- **Expand and collapse**: Support category tree expansion and collapse
- **Search function**: Support category name search