In the Additional Tools menu in the Builder, there is a section called Taxable Labor Options. This tool provides a quick, easy way to add or remove tax on all items in a project.
To use this option, go to the Builder and click Taxable Labor Options.
In the overlay that appears, you can select whether you'd like to tax labor on all items, remove tax on all items, or use the product's default tax status.
Select the option you'd like, then click Update.
This will apply your labor tax preferences to all items in this project.