> If someone knows of such a tool, I would love to hear about it.

Well, you probably not gonna like this but Emacs with Org-mode is excellent for managing Anki cards. My SR cards are not in some other medium — they are literally my notes. I can edit them freely; I can generate new content easily (e.g., using LLMs); I can turn any thought or a book quote into a card and vice-versa; cards are version controlled; I can embed formulas and code snippets; they are easy to search through; they are platform-independent; they are contextual — my cards are intertwined with additional notes, book annotations, screenshots, video links, etc — they help me study subjects with immersion;