If I open Proton and have 4 emails to read through, I would like to be able to open the first one and either use an up arrow key to navigate to the next unread email, or I would like an arrow as part of the top navigation bar to allow me to cycle through to the next unread email. Having to click each one is cumbersome on the desktop. You are able to physically swipe between emails on the app which works for the phone but would be clunky/unnecessary on the desktop.