By default extensions in a tab are alphabetically sorted. The new OrderEx add-in allows you to specify custom order for extensions. For example, by default OrderEx places .h extension before .cpp:
Custom extensions order
In the add-in, priorityExtensions array specifies order of extensions. Extensions not found in this array are placed after specified ones:
private string[] priorityExtensions = { ".h", ".cpp" };
It is highly recommended to use Tabs Studio v2.1.0 or greater with this add-in, otherwise custom ordering may be occasionally reset to default.
Download link: OrderEx v1.0.
Tabs Studio Blog (organizing Visual Studio document tabs) 