Smart Key - Dired Sidebar Mode

Dired-sidebar is an add-on Emacs package that puts dired in a sidebar and optionally integrates with various other packages. Use the Emacs package manager to install it and then invoke it with {M-x dired-sidebar-toggle-sidebar RET} and quit with {q}.

When in a dired-sidebar buffer:
  ACTION KEY or ASSIST KEY
     (1) within an entry line, the item is displayed for editing,
         normally in another window, or if it is a directory and
         ‘dired-sidebar-cycle-subtree-on-click’ is t it will expand
         and collapse the entry
     (2) at the end of an entry line: invoke ‘action-key-eol-function’,
         typically to scroll up proportionally, if an Action Key press; invoke
         ‘assist-key-eol-function’, typically to scroll down proportionally,
         if an Assist Key press;
     (3) on the first line of the buffer (other than the end of line),
         dired is run on the current directory of this dired-sidebar;
     (4) at the end of the first or last line of the buffer,
         this dired-sidebar invocation is hidden.