Freeform fillet
From TOI-Pedia
Surface > Surface Fillet > freeform fillet: Free form fillet is basically the same function as the circular fillet. The difference is the way the fillet is defined. With a circular fillet, the fillet is created between two objects. With the free form fillet the edges of the fillet is defined by curves on surfaces. This will create the option to make very complex fillets, with the fillets still tangency aligned with the surfaces.
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