Like I wrote, we will include a feature that lets people ignore this.
But all features that rely on the browser extension knowing what you know wont work then, obviously.
Until that option is out, the easiest way is just parse it as you did, hover over the words in the sentence that you do know and press 3 or K to mark them known. Only leave the word you dont know out.
In the beginning it may seems like a lot of work to mark all words known, but if you do it like I wrote above, it will take you like 2 weeks to teach the extension your knowledge. I looks like more work than it is in my opinion. And its really useful. Afterwards it unlocks a lot of the useful functions, like frequency exporting, find 1T, export 1T and all of that.