General

To achieve this you need to use only 1 table for the proposal items.

1. Create table – 6 columns by going from the editor menu Table->Insert Table. Your table should looks like in the screenshot. The tax % must exists in Setup->Finance->Taxes
2. While you have the focus on the table click on the icon Table Properties
3. A popup will be shown and like class name select Items Table
4. Click OK and save the proposal changes by clicking inside the editor Save Proposal
5. Click the button Convert and choose Estimate or Invoice the items should be auto added.