Hi,

First of activate the Margin form the sale settings, then in the sale order form you can see the total margin of this order near the total.

Once the margin is enabled, then in the sales form,

And if you need to see it in the sale order line, you can add field name margin to the order line, this field already defined in the model and it contains the line wise margin.

To add the field to order line, you can do it from the UI or you can do from the code.

Also you can get the same information from the Sale Report also, Sales -> Reporting -> Sales.

IF you need to export it as the order line itself, define a new menu and show the sale order lines, and to export it as excel you can use the export functionality.

Thanks