Yesterday I called BrainStorm Software directly in order to have
an explanation.
They Told me that 'The Manager' is like the MultiFinder for Mac.
They also told me that you can start applications from the Finder. Windows of each application are always displayed (but can be hidden). You can switch from one application to an other by clicking on his window or using key combination.
You can Cut and Paste between applications. The Manager works with all software GS/OS, Text or Desktop, 320*200 or 640*200.