<< Well you could use it for example to help draw a cylinder that had a central axis perpendicular to the surface of the sphere but partially submerged inside of it rather than sitting exactly on the tangent plane. Then with the cylinder intersecting the sphere you can intersect them.

it's that a sort of this I made some post above ;)
<< I can also draw a cylinder from the center of the sphere passing by the point I want then Curve / Intersect and killl the cylinder ! ;)

I don't deseperate to find something easy with the helper lines but for the moment
my above method of the move the Edit frame in Front view + Orient copy everywhere is very satifying and seems the more easy to do (for me) :)