If you are in the Plugins tab of the settings dialog and select a plugin, it is highlighted.
But if the list looses focus, there is no highlighting anymore.
It would be much better if there would be a "focussed highlighting" and a "non-focussed highlighting", for example in grey.
If you currently select a plugin, then shift focus by going to another window or e. g. pressing TAB to move focus to the "Configure" button, the highlighting is gone and you don't know which plugin you will configure if you press the configure button.
Of course normally there is not much time between selecting the plugin and pressing the button, but if you are distracted by someone else or whatever this can happen.
It would just be more convenient to always see what is selected.