Go to Tools > Settings > Interface > Shortcuts > Viewer mode > Random file > Shortcut for selected action > Custom
Assign it the custom keyboard shortcut: 0 ("zero" on your NumPad).
Now when you are viewing images with the Viewer, you can use:
- Left Arrow to view previous image
- Right Arrow to view next image
- 0 to view random image
Since the "0" key is next to the arrow keys on most keyboards, this makes it convenient and easy to use! Try it out yourselves, I think you'll like it!
If you bump into any bugs or strange behavior, please share it. This is still a very new feature for XnViewMP.