nnn is a terminal file manager
d detail mode toggle
t,u show size of directories and sort by size
. toggle hidden files
To start nnn in detailed mode with shown hidden files
$ export NNN_OPTS="dH"
$ export NNN_PLUG='p:!less $nnn'
Alt is used with plugin keys.
To open file using less (preview file): Alt+p
$ export NNN_BMS='d:~/Documents;D:~/Downloads'
The bookmarks are listed in the help and config screen (key ?).
b,D changes directory to ~/Downloads