I want to set a linear constraint, rename it and change the value. The drawing has no other constraints yet and it consists of just a straight line. When I try to change the value I get the error "A dependent expression cannot be evaluated." I then tried to add a new parameter and change the name or value of that, but I got the same error. I am new to the program, I used AutoCad before, and thus have no idea what could cause this problem.

(I use the DraftSight 2020 Enterprise Plus version.)