Now in 2018 a lot of phones have high screen-to-body ratio which forces companies to have software buttons. They dissapear when you play a game, watch video etc. but they appear again when you swipe from the edge of the bottom screen which is in the same position as the lines you can select. This situation creates problem if you want to remove one of the lines because the navigation buttons come up and you have to click one more time to make them dissapear (or wait) and only then you can delete the line you choose before.
My suggestion is to have an option to delete any selected line by double-tapping on it. It would solve the issue which I described quite easily and I think it’s pretty simple.