Question

How to remove all LineItems except the first one?

Answer

The following script will remove all instances except the first one:

if (Document.HasField("Invoice Layout\\LineItems"))
{​​​​​​
            while (Document.Field("Invoice Layout\\LineItems").Items.Count>1)
        {​​​​​​
                int itemsCount = Document.Field("Invoice Layout\\LineItems").Items.Count;
                Document.Field("Invoice Layout\\LineItems").Items.Delete(itemsCount-1);
        }​​​​​​
 }​​​​​​

Please use such script in Event Handler "After Document State Changed" (Project > Project Properties > Event Handlers, choose the After Document State Changed section, and press Edit Script):

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