I develop a complex LOB windows desktop application. Right now it has only one feature say A. All menu and toolbar is for A. You can open multiple document related to feature A, each within a Tab control. When I say document I mean logically. Each tab page has a tree view on the left pane and screens on the right pane that changes when different nodes on the tree view is selected. Right side pane can have list view, buttons, drop downs, radio boxes etc.
There is a desire to enhance this application to have feature B, C etc. The goal is to make this Application the single app for all of the enterprise. Different features are mainly used by different departments but there is some cross over. The idea proposed is to create a Tab control for each feature and then documents in another set of tab controls. i.e. two layer of tab controls. I think there are better way of doing it.
One option is to use multiple horizontal/vertical tabs like in Microsoft OneNote 2010. Another option is to use the Outlook 2010 with tabs on the left column. There is a possibility that doing something on a doc under feature B would create a doc under feature A and switch to it.
I want some alternate ideas to nested tab control as shown below.