You can create fillet curves among several curves using Fillet Curve.
To create fillet curve:
Click Fillet Curve (Curve toolbar) or click Geometry, Curve, Fillet Curve .
You can select edges or shared vertex to create fillets between two neighbour curves. Normally, all source curves should locate at the same plane. If selected edges are not strictly located in a plane, check "Project to Plane". "Try to Trim" is to trim curves mutually before fillet.
a. Two circles (radius=1.0) trimmed with each other b. Create fillet curves between each circular arcs. The fillet radius is set as 0.7..
c. Four bspline curves intersect with each other d. Fillet results after checking Try to Trim