The following is slightly off topic although it fits more or less under the same heading.
Highlighting would also be very useful on the tactical map! The reverse should also be possible, i.e. click on an icon in the bar to select the corresponding unit on the battlefield.
This helps to answer the question: Which unit(s) should I try to kill first? The AI "knows" this but for us humans it is almost impossible to tell those units (of the same type) apart. Units of the same type are not equal, by the way. One of them was hastened, another slowed down, one is wounded, ...