WordPress ‘After the Deadline’ Proofreading technology needs an update – can’t add words to user dictionary

I’m relatively new to WordPress, used it for a few projects but don’t generally author content in its online editor. I’ve been wondering for a while how to set the dictionary language to Canadian English and how to add words to a user dictionary, both things that are standard since forever with any decent editor. I finally got around to checking the WordPress online help for proofreading and it turns out you can’t do either:

Can I add words to the dictionary?
No, but you can add phrases to an ignore list so they don’t show up as errors.

Do you differentiate between American, British, and Canadian English?
Not yet. For now, American, British, and Canadian variations of words are in our dictionary.

WordPress has so many great features it is really hard to understand why they haven’t bothered to add these two features. Here is a shout out to the community, is there a solution?