Sheet-related (building or otherwise) is best handled in Character Sheets & Compendium forum. Regarding your question; I'm not sure you can actually delete attributes using sheetworkers or otherwise once created. You can delete non-repeating attribute manually from the Attributes & Abilities tab, or using the modify/delete option for repeating attributes. (or removeRepeatingRow() via sheetworker) Setting an attribute's value to an empty string, i.e "" probably has the least impact on a sheet. Curious, "unused attributes..." are these attributes no longer needed at all? Have they been removed from the latest HTML? If so, only the older, existing sheets may have the attributes, but newer sheets will not. Do you need to migrate older attribute data to newer ones? What is your goal/use-case?