1 - Just click your first point of your line somewhere then move your mouse and Write 4 5 6 in the Box bottom screen for x,y,z target! ;)

2 - Just draw your line then Click your line on an "hot point" (start - middle - end line) then move it in any direction and write on the numeric keyboard your wished distance (like 17 Enter in the "d" box screen bottom ! ;)
Your line will be move anywhere in a circular limit of 17 unities from your first snap click on your line!