Initially, this container will display all the WPS file types that have been defined on your system. However, &xwp; adds functionality to that concept in that file types can form a hierarchical tree. This container supports drag and drop within itself so that you can re-arrange your file types to form such a tree. For example, you can drag the "&os2; Command File" type onto the "Plain text" type to make it a subtype (that is, all "&os2; Command Files" will also get the associations for "Plain text").
This container also has &popmenu;s to delete types, create new types, and for
"lazy" drag'n'drop ("pickup" and "drop" items).