Hy Jack,
i can not provide a complete solution for your request as the totals are not saved to a table and the total value is not a column that could be added with the standard to the sale order list form.
As a compromise you can do this one for open Sales Order (and even all Orders). You need to have "saved views" activated in the features.
Open the Sales and marketing/Sales Orders/"Open sales order lines" list page.
Here you can add the column "Net amount"
On the "Sales Order" column right click and select "Group by this column"
On the "net amount" column right click and select "View column totals" as "Sum"
Save the view as a personal view and distribute to user or security group if this is good for your requirement.
May be the "net amounts" are not finally correct because of charges or discounts on line or header level.
Additional you can adjust some filters for the "open sales order line" form on the "advanced filter and sort" form.
Just adopt you selection for the Line status and order type you want to see on the list form.
E.g. filter for all order types and all order status looks like this:
When you have confirmed the filter save this as a "personalized view" with a fitting name, and even if you want to be this the standard view for the "Open sales order line" form select "Pin as a default".
Now every time you select "Open Sales Order lines" menu item this form will be opend and display all sales order lines (not even open lines) and the sales order lines grouped by Sales order and summed by net amount.
Isn't that fantastic?
I think it is good, but for now it is not complete as we can not collapse or expand all grouped sales Orders, this has to be done by each sales order.
You can also add some sorting criteria as you want to see to newest SO on the top.
Hope this helps.
Herzliche Grüße / kind regards,
Andreas Raithel
D365FO Solution Architect