You can change or set up new buttons for input very easily in UE4.

1. Click on the button "Edit" (in the top over the Viewport)
2. Then click on the point "Project Settings"
3. Then a new window should open. On the right should be list of different Things to configure for navigation
4. Under the Headline "Engine" is a point labeled "Input" click on it

Here is the current layout of buttons (v1.0) to control everything I set up