I built a native flashcard app for mac that includes spaced repetition. You can close the main window, so it is not in the way and just select add flashcard from the top right menu bar in whichever application you are in
Anki is good, but the problems that I had with it was that I was not learning the flashcards well enough on the first day to to recall those flashcards on subsequent days and it took too long to make flashcards, so I made myself a flashcards app.
http://flashcardmax.com/download
I had the problem where it felt too time consuming making the cards and I just wanted to start off learning a few cards at a time, so I made my own solution. Its free
https://www.flashcardmax.com/download
https://apps.apple.com/us/app/flashcard-max/id1430950704