1. Open 3D mission editor.
2. Place any unit.
3. RMB on unit, select "Attributes..."
4. Expand "Object Type" section.
5. LMB on any item in the "Type" list.
6. Press up key repeatedly, note behaviour of tree view list when pressing up key when the selected item is at the top of the visible items.
7. Press down key repeatedly, note behaviour of tree view list when pressing down key when the selected item is at the bottom of the visible items.
(optional steps to observe list box behaviour)
8. Close object attributes dialogue.
9. Place a trigger.
10. RMB on trigger, select "Attributes..."
11. LMB on down arrow next of "Activation", to open list box.
12. Press up key repeatedly, note behaviour of list when pressing up key when the selected item is at the top of the visible items.
13. Press down key repeatedly, note behaviour of list when pressing down key when the selected item is at the bottom of the visible items.