This allows you to display multiple trees next to each other to compare them. You may also display different regions of the same tree using multiple windows.
To open a third view, use this function from the second window (and so on). Currently this is limited to 5 parallel views.
When closing the first ARB_NT main window (that one with the big red 'X' button), your ARB session will terminate. Closing secondary ARB_NT windows (those with a blue 'X' button) will not terminate ARB.
Secondary ARB_NT windows contain a reduced set of menu functions, mostly those which somehow interact with the currently displayed tree. Each windows' menus refer to their own selected tree.
Macro functionality is not yet completely working for secondary windows, i.e. sometimes macros refer to the first window instead. If you encounter problems with that, please inform us about the bug.