Here a general Joint after a Cut for have a general gap...(3dm linked) Joint = Blend in French language... sorry for that!
You can of course take the Bulge that is satisfaying for your use...
(align the 2 points at the end of the Joint function) the "Blend" !!!

https://moiscript.weebly.com/uploads/3/9/3/8/3938813/fillet_joint.3dm

But I believe if you have the original piece before your gap (i am a little lazzy for rebuild the original piece :) that a Variable fillet is possible!
(make the minimum general fillet admissible then add variable fillets anywhere you want on the other parts of the path)