Yes, you can edit the list or delete unused items from the list. From any constituent record, locate the dropdown lists (also known as a picklist) and click on the arrow in the drop down box. Click on <New/Edit> to open a new window for editing. 

To edit an item, click on the edit icon (pencil and paper) and make the desired changes to the Value in the space provided. Click Update to save the changes or Cancel to return to the list without making a change.

Before you can delete an item, ensure that it is not currently in use for any constituents. You can create a view on the Constituents grid that includes a query or filter for the item to search for any records that have been assigned that value. If you do find any constituents with this value assigned, you will need to remove it from their records prior to deleting the value. You can do this one at a time or, for some fields, you can use Batch Update.

Once you have ensured that the value is not in use, you can click on the trash can icon to open the confirmation window. Click Delete to remove the unused value or click Cancel to return to the list without making any changes.

When finished making your changes, click Close at the bottom of the window to return to the constituent's profile page.