Is this possible?
Have an editable checkbox dropdown? over time items would be added to the list with a widget, that the user can check?
You can base the values on a field in a table and add/remove items from the list by adding/removing records from this table. The management of this list can be supported with scripts to make it easier for your users.
Keep in mind though that if you remove a value from the list, this does not change the data stored in this checkbox formatted field. If you have Apple as a value and then later remove it. "Apple" will still be stored in any records where this value was selected, but the value will not be visible to the user on your checkbox formatted field. If removing a value from the list means that you also want to remove the value from all fields where it was selected, you'd need to write a script that does this for the user just before deleting the record in the table of values.
Retrieving data ...