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No, not that I know of, is there a way to convert a spiro spline to a path, and then back again (there are very few instances in Inkscape where you can convert something to a path, and then back to the original). But I CAN think of a way to achieve what you want. Actually I do this all the time! I love to play with the spiro splines. What I do, is once I have a spline that I want to keep, I simply Duplicate it. Then I can convert my original to a path, and do whatever I want. And I also have my duplicate, which is still a spiro spline, and I can continue tweaking it further.
Of course I do end up with bits and pieces of things that might later need to be assembled. But Inkscape's Snap functionality is very helpful with that part. Also Layers, if it's going to be a very large, complex image.
Will that work for you?