Isometric Parellel Lines

Is there an easy way to do parallel lines using the isometric grid display?
If I use some trig, I can accomplish this, but this requires too much extra time.

An iso parallel line of 10 would be cos(30) x 10 = 8.88.

I am not sure what you are asking for. Do you want a parallel line with an offset of 10 to any given line automatically according to the isometric grid with 30 degrees offset? (unlike your example). No, that's not possible.