I accidentally clicked some button which added all the words in an article to my “known words”. How do I reset and start over?
I could be wrong but I think you have two options.
One is to read through the lesson and LingQ any words you need. This will subtract them from your known words total.
The other option, a more drastic one, is to go to your Accounts page, and delete the language and start again.
In case you don’t know how to LingQ words from that state:
highlight the individual words like you would any other text.