1. Select the drop-down cells
Highlight the cell or cell range in Excel containing the drop-down list you want to modify.
2. Open Data Validation settings
Click the Data tab in the top Excel toolbar, then choose Validation.
3. Edit the list items
Click into the Source field where your list items are defined. Make your changes—for example, add a new item like Blocked.
4. Save your changes
Click OK to confirm and update the drop-down list.
5. Verify the updated list
Click a cell in the edited range and use the drop-down to view your updated list items.