Thank you for your support and valuable input for resolving this issue of designing a coil consisting of straight parts combined with bends with constant radius. The item is a heat exchanger and the bending machines are are capable of producing items with straight parts or bends with constant radius. In order to produce the coil which has a continuous change of bending radius, we need to convert the design into parts suitable for manufacturing.
The trick that resolved the issue was the WB curves and draft, creating the center line of the item by connecting end points of 3-point arc (macro) with straight lines, followed by a sweep.
The section feature identified by Hammax is far more simple and less time consuming, compared to the solution we used.
Thank you so much for your contribution and assistance!