In LTspice a SPICE Directive is text placed onto the schematic that passes directly into the netlist. It may be entered either as a single line or as a block of several lines of text. Since ENTER closes the text edit box, a new line must be started by typing either ctrl-ENTER or ctrl-M.
The text edit box may be accessed either via the drop down menu item: Edit => SPICE Directive or by pressing its Hot Key, if one is assigned ("S" is the default). Also, the Simulation Command SPICE Directive (drop down menu item: Simulate => Edit Simulation Cmd) is a dedicated dialog box that may also be used to create this particular line of SPICE text.