The Customize window mouse trailer seems to react oddly on my system.
The trailer goes very slow and sometimes remains visible as a shape.
This happens even when Biblioscape is the only application running.
Once an action is completed part of the trailer remains visible on the Customize window. (Perhaps somebody else could also try this and report)
The Customize window remains in front of any other application given focus in front of Biblioscape. e.g. Windows Explorer.
Ian