This mostly works with Mochi - you can paste PDFs etc into ChatGPT and the Mochi markdown format is simple, so it can generate flashcards for you (I have the format explained in my system prompt so I don't have to re-explain it every time). This synergizes nicely with the fact that you really want to understand something before you make flashcards from it.
If you pay for Mochi you also get API access, so one could make a ChatGPT wrapper which adds the cards for you. But since I like to review the cards manually before adding I don't mind the copy paste step.