Mark,
No, this is not available yet, but you can preview a recipe in a window (Right click on the recipe and choose "Preview in New Window") while still having another tool open.
I'm thinking for version 2.0 I will have all of the options available (perhaps like Firefox where you can Shift-click to open a separate window, and Control-click to open a separate tab with tabbed browsing, or click to just open a tool in the same tab like it does today). In addition there might be options where one could override it so all tools open in a separate window, or all recipes open in separate tabs.
Also - I've been experimenting with split tabs where you could display two tabs side by side in the same view -- for example have a recipe and tool open side by side in separate panes.
I'm just starting to experiment with new interface options - but I want to make it more flexible than it is today. For example I have two screens on my computer and would love to be able to do multiple frame displays when working on recipes.
Cheers!
Brad