[Slack] has a couple of useful keyboard shortcuts for navigating between unread
channels. Unfortunately these use an awkward combination of keys involving
multiple modifiers and an arrow key (<span class="keyboard-shortcut">⌥⇧↓</span>
and <span class="keyboard-shortcut">⌥⇧↑</span>). Additionally these shortcuts
are not exposed in the menu bar, meaning they are not able to be modified with
the [built-in support for such customisation in Mac OS X][custom-shortcuts].

[Slack]: https://slack.com/
[custom-shortcuts]: https://support.apple.com/kb/PH18418

I have made a feature request for this to be addressed. Until the time that
happens, if at all, the following [Karabiner] config can be used to change the
next unread shortcut to something more sane. I chose
<span class="keyboard-shortcut">⌘J</span>:

<script src="https://gist.github.com/wezm/05210d76660e735944a7.js"></script>
[View Code][code]

[Karabiner]: https://pqrs.org/osx/karabiner/
[code]: https://gist.github.com/wezm/05210d76660e735944a7