Specialist Improved Thermal Binocular - How to tag enemies?

Solution 1:

I have not used this star card that much, but when I have, I've learned that it works best when there are multiple enemies in the line of sight. You can tell that they are in the line of sight because you can see the class indicator above their head. Then hold the fire button down and it should mark them.

I used the binoculars more in the first game, when it worked in a similar way, and there would be a small circle on enemies that could be tagged, and when you held the fire button down it would fill up and they would be marked, and my guess is that in the more recent installment it works in a similar way.