"Display level map" command (alt+l) isn't listed in the manual
You can only view it in the in-game help
I tried searching for the command "display level map" in the manual, but couldn't find it. However, I did find it in the in-game command list accessible via "?" (it's listed there twice in R69 for both keybindings). It should be listed between "display killed monsters" and "display message buffer".