Outliner
This is a building block we have used for almost two decades to have quick tracking of armies, constructions, and other things in progress. In EU5, we now have two versions of the outliner, where you can have a simpler one if you feel the normal one is too noisy.

It's a quick way to select units and change things on the fly.

And of course, we got settings so you can toggle what you want to be able to see: