This field is used for the system to know which lines need to be in a single sale.
For example, if you add an Invoice_Number column in the Excel import file, then all lines from one sale will have the same Invoice_Number.
In this case, you need to select Invoice_Number option in the “Group Sell Line By” dropdown field.
“You cannot select a field twice” Issue and Solution:
You may encounter this issue while you import an Excel file using the Sale Import feature.
This issue happens when the same option name is chosen for multiple columns in the import table
If you want to remove any column during import, you can select the SKIP option in the dropdown.