DiscordApp_jumpToUnread.js

function handleKeydown() {
  var unreadSelector = '.channel.channel-text.unread > a';
  var unreadIndex = 0;
  var getUnread = () => document.querySelectorAll(unreadSelector);
  var numUnread = getUnread().length;
  return function (e) {
    // Hotkey is CTRL + B (case insensitive)
    if (e && e.ctrlKey && e.keyCode == 'B'.charCodeAt(0)) {
      var newLength = getUnread().length;
      var unreadDelta = numUnread - newLength;
      numUnread = newLength;
      unreadIndex -= unreadDelta;
      unreadIndex = unreadIndex >= newLength
        ? 0
        : unreadIndex;

      getUnread()[unreadIndex++].click();
    }
  }
}
document.addEventListener('keydown', handleKeydown());