The issue is about Variable property dialog in the BPEL editor. This dialog appears when user either create or edit a
variable. The dialog contains the tree with type chooser. It is intended to specify a type of the variable. Now the
chooser has some limitations, which has to be overcame. 

-- It´s impossible to choose a type from another projects according to projects' dependency.

-- It´s impossible to choose a type from a schema if it is imported or included to another schema. Now there are root
level schemas only. The schema node has to have the "Referenced schemas" node inside in order to provide access to such
schemas. You can see WSDL or Schema editors for example. 
It is mostly important in case, when a top level schema includes another schema which doesn't have target namespace. If
the user gos to the imported schema through the "Referenced schemas" node, then the chosen type should get the namespace
of including schema. It looks like the only way to resolve such case.

It's also suggested, but is still arguable, to get rid of the "Show Imported Files only" check-box. The chooser's tree
should show all available files. Those which isn't imported can be shown not at the root level, but be moved to the
special folder: "Not imported files".