I currently run Spotify in Dark Mode on my Windows 10 desktop. This is the electron version, locally installed to my user AppData due to admin permissions.
There is nothing in the User experience of Spotify that indicates if it has focus or not. Further, because of the positioning of the minimize/maximize/close buttons, sometimes it is hard to pick them out - especially when other Electron apps are also running. For me, this is most noticeable when I am running Spotify and Teams on the same window. It is nearly impossible to tell which minimize button is the correct one.
I attempted to change my Windows accent color, to see if Spotify would reflect that change. However, it did not. It is still just a black box, with no border around it.
Your Idea has been submitted a while ago, and unfortunately hasn't gathered enough votes (50 votes within 3 months) to keep it active in the Exchange. Be sure to know that this does not mean that your Idea has been declined by Spotify.
Don't worry, your Idea will still be able to gain more votes, and may get a Live Idea status if it receives enough of them.
For more info on how the Ideas Board works, click here. 🙂