When customizing MicroStation's user interface, it's useful to be able to appoint an icon in a tool palette. That leads to the Define Icon for Tool dialog...
The above dialog has a curious behaviour: the mouse scroll button doesn't scroll the view of icons. Instead, it remains focussed on the Option Button labelled Look for icons in.
If one uses the scroll bar on the right, then the icon view is scrolled as expected. But, using the mouse scroll button changes the selected icon source. Since most of those are empty, the consequence of using the mouse scroll button is to clear the icon view.
That behaviour is counter-intuitive, confusing and irritating. Please fix it.