Opening a new window in calibre, and closing another window

Can I close the current window on calibre (with x number of titles) and open a new window without any books, in order to start fresh?

(Think of a word processor: One closes the window for the current writing project and opens - or creates - a new window for a different story.)

I wish to keep all my Kindle purchases separate from all my other ebooks, and without slowing down - or slogging through - all the other stuff.



Don