This is a very pedantic question. I'm using Ubuntu 16.04.3 LTS on my desktop and recently switched from Unity to Ubuntu Gnome (3.18.5). I'm using the excellent Dash to Dock extension.
My pet peeve is that when I open an app that I installed, it is not highlighted with a blue line in the dock, unlike system apps like Terminal. For example, the Brave browser that is open here -
Moreover, if I click on the icon for Brave again, it closes the running instance and starts a new one. If I enable "Show Running Applications" from the extension settings...
... the running application is shown as a new instance in the dock, unnecessarily extending it.
How can I get my system to highlight the running app at its place in the dock itself?
EDIT : This lack of highlight only happens for apps that I've installed later - using snaps or PPAs.