A flexbox based application layout, where the content panes can be resized and reordered with drag and drop. Note: Vertical containers can only be split horizontally, whereas horizontal containers only vertically.
Demo available on speich.net
Drag and drop tab onto another tab (add):
Drag and drop tab onto vertical overlay (split):
Drag and drop tab onto horizontal overlay (split):
Drag and drop tab onto vertical divider (split):
For more information read my article about flexbox layout on hacks.mozilla.org.
Requires dojo.js and NodeList-traverse.js