This allows you to import line items from another Sale or Purchase document. This can be useful when you have created two documents that you would like to combine or if there are line items in another invoice you would like to duplicate in this document.
Once selected a dialogue box will open prompting your to search for the document you would like to import the line items from (you can search by number of name of the document). You can then choose which heading on the currently open document you would like those line items to appear under. Lastly, choose the line items from the other document you would like to import.
This process will not remove the line item from the document that you have copied them from. It will only create duplicate copies in the existing document.