...
- Navigate to the System Definition → All tables;
- In the Name field type 'incident' to filter the tables containing this word;
- Click on the table 'incident';
- Scroll the page down to the 'Column' tab;
- Find the row that contains containing the column name where you want to create a new option, and click on the table name in that row;
- Find the category or subcategory you want to delete and click on it;
- Click the Delete form button at the top of the page to delete the category or subcategory.