Unfortunately not. But you could open your domain model in the web modeler and work on the desktop modeler at the same time. Not ideal but could work in case you want to see the reference you need to quickly continue developing. But if you want to do changes you have to either do this on your desktop and then synchronize or the other way around.
Although you cant open the domain model in a separate window, you can have mutliple tabs open in the modeler. Luckily I use a big enough screen that everything isnt scrunched together. I recommend being in full screen mode when you do this (F11).
alternatively, if you use double monitors, in the past i've stretched the modeler between both monitors with two tabs open to make it appear as if I have two separate windows open.