as you can see in the picture, there is a file icon in the tab bar with the filename next to it.
In my own vault, I am using no custom theme, and no hider or anything like that, and my tab bar is different, I do not have the icon nor the file name like it is in the picture.
I am trying to get it there but dont know how to achieve as it is in the picture.
Things I have tried
I tried couple of themes and CSS, but none worked.
I don’t know how that (2 year old) screenshot achieved icons. But you might be interested in metadata menu which can achieve this by setting up file classes: