It's not possible to displayed normal EV_WIDGETs (especially EV_COMBO_BOX)
vertically in a tool bar for the moment. So we don't display them when a tool
bar docking vertically.
 
After customize a vertical docking tool bar, the EV_WIDGETs should not
displayed neither. It's a bug which fixed in the revision#69480.

Thanks for your report.