is that a custom screen? There is no top menu customers, there are Sales/Sales Orders/List Open. From Sales/Customers/Workbench, that has orders on it?
not sure the screen you refer to, but if it's just open sales orders it has meta sql that drives that screen:
ORDER BY cohead_number;
that is the default order by for:
-- Group: opensalesorders
-- Name: detail
You could make that a date and ASC or DESC to get them to load like you want ( if that is the screen).