Hello Michael,
A little request here, im currently working on a watch and I always found me drawing a line from a snap point (usually on a circle curve) then rotate that line (copy enable) to do the other symetrical part. Like doing a crosshair, you draw a circle, then line from the center to the circle snap quad point on your right, then mirror or rotate copy to make the other part on the left, same for up and down.
I cant start from another point, usually I dont have snap points everywhere and im not on the grid.
It would be could to be able to skip that step by having a "Line from center point" tool under the line tool.
You first click for center, then move the mouse, the line is previewing just like the Line tool, but you also see the symettry previewing.

If anyone think it would be usefull, comment on it.
Have a good day !

(ps: the result would be a single line and not two separate lines, maybe the center can also be seen when "show points" is activated, a 3 points line, wich can be transformed to an arc just by moving the center point)