I just received an email asking me how to remove stocks from a watchlist. It's pretty straight-forward but it may not be obvious if you're using a mobile device. If you're using a desktop or laptop computer (or maybe even a large tablet) you'll see a trash can icon over on the right side of each stock's row. Just click the trash can icon to remove the stock from the list -- note that the table scrolls horizontally & you may have to scroll it to see the trash can icon. The pencil icons allow you to edit the stock's details (The note for a watchlist... stop loss values, number of shares, entry price, etc. for a portfolio).
If you are on a mobile device it a little trickier. For most of the tables on the site, columns get hidden to conserve space on mobile devices. You'll be able to tell when data/columns have been hidden because you'll see a plus sign on the left side of each row. Tapping the plus sign or just tapping anywhere in the row will expand the row and show the hidden columns. Once the row has been expanded you can click the "+" to reveal the trash can. See below: