Force TreeSheets to open a new file in a new window instead of tabbing?

view story

http://unix.stackexchange.com – I am using the application TreeSheets, which is something like Excel on steroids. And I want to be able to view two "spreadsheets" side-by-side. Sadly, the application itself does not offer this as an option, and automatically puts each newly opened document in a new tab, without even the possibility to "arrange windows" within the main application window as known from Microsoft Office products. Is there any trick to trick the application into starting a second time? Maybe something on a window manager level? (I am using KDE + xmonad; it is OK if it is a hack which happens to produce somethi (HowTos)