Posted by Gary S on Jul 28, 2022; 10:37pm
URL: https://forum.librecad.org/Alternate-for-relative-coordinates-tp5721933p5721936.html

It is in Using the Keyboard in the Fundamentals section.

Try typing this series of commands:
   li
   10,10
   20..20

The first line, "li" is the "2 Point" line command, the next line places the first point at (absolute) 10,10.  The third line, "20..20", will place the next line's point at relative 20 up and 20 left (or at 30,30 absolute).  The command line output window should show:
   Accepted keycode: li
   10,10
   @20,20

"20..20" is translated to "@20,20".