I’m not sure if the site did this before the last update, but I’ve noticed that when I’m ready to delete a lingQ that is known, lingQ also removes that word from my known word list. Is there a way to prevent this without re-highlighting the word and clicking known? I like to see a word without the availability of aid once I know it well.
Deleting a LingQ will cause it to be ignored as well. To make it Known you can, as you say, re-highlight it and click “Known”. However, we don’t encourage deleting LingQs, since it’s very possible that you’ll forget a word even if you mark it as “Known”. This is the benefit of having lots of Status 4 LingQs, in that all the time you put into creating those LingQs isn’t wasted 
That’s true. Thank you!