HaroldPD

Avoiding 'Decorating Cards' appears to be your unique selling point, as it is the most prominent headline text on your website and mentioned twice in your text here.

The meaning of this is obvious to you, while being obscure for me. Perhaps have a link within your site to expand on the meaning of 'Decorating Cards'. ( I assume it is prettifying. Perhaps it is initial card creation, or bulk loading. Perhaps it is includes other steps. ) Describe how your software is superior to putting minimal effort into using default anki cards with text and images.

Epsilon editor from https://www.lugaru.com/

Stable and fast with EMACS-style behaviour and key assignments.

Has C-like extension language named EEL that you could convert / re-write the vundo tree in.

I recommend Brother Black & White lasers. (Brother seem to want the business and don't try to abuse their customers.)

Epsilon https://www.lugaru.com/

Comes sufficiently close to be worth testing the free trial.

I don't know the file size limit, but it handles multi-GB files.

Does not fulfil the hex requirement. Recognizes and edits binary files but is not a hex editor. The previously suggested https://hexfiend.com/ looks better for that.

Unlimited line length, and can either horizontally scroll long lines or wrap them for display purposes.

Fast regex.

Unlimited undo/redo, including search/replace.