The system will automatically sort the categories in the item catalog but you can change that order to make it easier for your specific workflow and pattern when adding line items and categories to the job.

To access this, go to Settings > Item Catalog > Sort Categories. Simply click and drag the categories in the order you want, and click the blue "Save" button.

When you go inside a job and press the blue plus sign to add line items to an estimate or invoice, the new order will be present.