I just tried both of the followings:
noremap <del> j
and
noremap <del> gh
None of them make any different in normal or command-line mode. Del key works as expected in command-line mode and doesn't do anything in normal mode.
I just restarted my system and noticed that backspace is working (moving up one level just like h). But this is what I have in vifmrc:
noremap <bs> j
noremap <c-h> j
How does j make it go one level up?