I would like to create hover effect for two elements: when mouse over both of the two elements, only one element get filled with different color, the other element remain the same color.
Apply the Interaction Styles desired to each widget separately. Group them with CMD/CTRL + G. Then right click the grouped widgets and select Trigger Interaction Styles from the contextual menu. Now when you hover any widget in the group it will trigger the mouseover styler for all widget in the group.