Extrude 2 sides option:
consider adding 2 side option to the extrude tool so that a curve can be extruded at different distances from each side of the curve. This eliminates the task of extruding from one side then again extruding from the other then performing a union command. It creates one object in one extrusion.
fusion 360 has a simular option in its extrusion tool. I am sure shapr3d can optimize this to improve the user experience.