Tab browsing has been a dominate way to surf the net, and has been proved efficient with organizing many windows.
I suggest LibreOffice introduce tab browsing to manage opened documents to reduce the amount of windows when we are in heavy use. The switch between documents will be more easily.
For example, all the Writer windows become organized in one main window, and use tabs to switch between them. So does Impress, and so on.
*** This bug has been marked as a duplicate of bug 37134 ***