When adding a loft to the edges of an existing surface or solid, you can set the continuity using Start Magnitude and End Magnitude.
Procedure:
[1] Prepare the existing loft shape.
[2] On the Surface tab, click [Loft Surface].
When creating an additional loft, the elements selected as loft curves must be surface edges.
If the second selection is also a surface edge, you can set the End Magnitude.
If you select the original loft’s sketch (profile lines), Start Magnitude cannot be specified.
[3] Select the surface edge and the sketch or other geometry to which the loft will be added. Then select Start Magnitude:

Creates a loft that connects curves directly in a straight manner.
Tangent (G1): Creates a loft tangent-continuous with the original surface.
Curvature (G2): Creates a loft curvature-continuous with the original surface.
Please refer to the video below.
IC-147