Bug 4240 Can't edit class path entry (1GKEPIF)
There is no way to edit an existing entry for a library on the Java Build Path project properties page (other than editing the .classpath file directly). NOTES: EG (9/22/2001 11:42:11 AM) this is particularly annoying for variables. we should have an Edit button when a variable is selected.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/LibrariesWorkbookPage.java
LayoutUtil.doDefaultLayout(composite, new DialogField[] { fLibrariesList }, true, SWT.DEFAULT, SWT.DEFAULT);
		LayoutUtil.setHorizontalGrabbing(fLibrariesList.getListControl(null));
		
		int buttonBarWidth= converter.convertWidthInCharsToPixels(24);
		fLibrariesList.setButtonsMinWidth(buttonBarWidth);
		
		fLibrariesList.getTableViewer().setSorter(new CPListElementSorter());
		
		fSWTControl= composite;
				
		return composite;
	}
	
	private Shell getShell() {
		if (fSWTControl != null) {
			return fSWTControl.getShell();
		}
		return JavaPlugin.getActiveWorkbenchShell();
	}
	
	
	private class LibrariesAdapter implements IDialogFieldListener, IListAdapter {
		
		
		public void customButtonPressed(DialogField field, int index) {
			libaryPageCustomButtonPressed(field, index);
		}
		
		public void selectionChanged(DialogField field) {