One of the things I missed most from vim's fuzzy finder plugins is the ability to open a result in a new split. So today I decided to take a few minutes today and look for a solution. Turns out I'm not the first to want this, and came across this issue that has a nice solution.
Turns out, all you need to do is add something like the following to your keymap (goto Atom → Keymap… to edit it):
'.fuzzy-finder atom-text-editor[mini]': 'cmd-right': 'pane:split-right' 'cmd-down': 'pane:split-down'
Now when you're searching for a file, you can hit ⌘→ to open it in a new pane to the right, or ⌘↓ to open it in a new pane below. (You could probably figure out the other directions, but I find these 2 are what I want do do 99% of the time). Pretty handy!