Typically, people organize papers on their desk as piles, and move all of them simultaneously. Malone  found out that users like to group items spatially. We claim that providing multi-window operations on groups of windows can decrease the cognitive load on users by decreasing the number of window operations.
In elastic windows multiple operations are achieved by applying the operation to a group of windows at any level of the hierarchy. The results of the operations are propagated to windows inside that group recursively. This way groups of windows can be packed, resized, or closed with a single operation.
Another way to achieve multi-window operations is to select an operation and apply it to windows rapidly in a serial manner.
Operations like multi-window open, close, resize, pack, and unpack enable users to change the window organization quickly to compare, filter, and apply the information. Pack and unpack operations on groups of windows help users to filter-out unnecessary information as well as enable fast task-switching. Packed windows still appear in the same location preserving the spatial cues. This helps users to recall the window contents and reminds them of unfinished tasks. When a packed window is unpacked all the windows in the group are restored to their previous sizes, so that users can reconstruct their previous working environments easily.
Hierarchical organization and applicability of window operations at any level allow rapid task-switching, even when the number of windows is large.