Drag-and-drop of toolbar actions is a nice feature that currently is
basically hidden to end users. The only way to enable it is to open the
"Configure Toolbars" dialog (!). Some applications (e.g. Kate) open the
dialog as modal, so there is no way at all to use this feature in such
apps.
This patch adds a checkbox in the toolbar context menu to enable the
drag-and-drop feature. This should improve its discoverability.