@MrLavender @cscs
I think I expressed myself poorly.
Normally, when a program is open in the taskbar, it is highlighted to indicate that there is an instance of this program running on this desktop. It is usually even more highlighted if it’s the program with the window currently in focus and turns orange if it’s a window that requires our attention.
I have the same settings as you on the Icons-only Task Manager (I assure you, even though my interface language is French). (cannot add image because i’m not trusted enough)
I see no parameter that has to see with window highlighting 
To be even more explicit, first image on this topic show Discord on focus, and the taskbar doesn’t even indicate that the program is opened, in focus or anything…