You can make slight changes to your item catalog as needed in your estimate without affecting your Settings Catalog.
To add a category on the fly, click on one of the line items you want, and then Shift + Click on the Category Name to edit it.
To add a line item on the fly, you can choose from your item catalog by pressing the blue plus sign or you can just click on the category you would like the line item to appear in and a pop-up window will prompt you to enter a new line item.
You have the option to “Add to Item Catalog.” If you leave this option unchecked, it will just add the line item to the current job. If you check this, it will add this item to the Settings item catalog for future use.