JL82,
I am unaware of a tube bending "add-in" for GMD. But, the issue usually boils down to avoiding structure and maintaining a clear distance to allow for thermal and/or vibration effects. Right?
If my "run" is (say) 2 inch OD tubing and I need (say) 4 inch clearance to allow for thermal and vibration effects, then I need a path that stays 5 inches from the structure, right? Whether it is better to construct reference geometry or a 3D path is really your choice. I virtually always construct reference geometry as an in place new part at the assembly level. The main PITA is constructing the axis of revolution for the bends. There is no easy way to convert that to a standard tubing bend drawing. It is a back to fundamentals effort.