adding sum icon + function

Hi, 

You do it in the page designer by adding the fields under “Summary”.
 

Thanks, and how can I add this horizontal tab? 

On that page there is only one list making up the whole view. And it seems like if there is only one section, the title is not displayed. And I can’t find a setting för displaying it. But I did a quick work around. I just added another object in the page designer, in this case a “markdown text” object. And then I made that object not visible. Now the title bar is visible. 
 

can I add this Inventory transaction history in Purchase Order tab?

*under attachments

my goal in this case is to add through Page Designer PurchaseOrderInvoiceList and InventoryTransactionsHistoryList in entity PurchaseOrder, it is possible?