The rotation at a spline point is defined by the spline point’s tangent and up vector. So currently you can set the point’s rotation in blueprints by using the desired rotation matrix’s up vector as input to the spline function SetUpVectorAtSplinePoint and the rotation matrix’s forward vector as input to the spline function SetTangentAtSplinePoint.
Additionally we will add a blueprint-callable spline function SetRotationAtSplinePoint for UE 4.26 which encapsulates this logic for convenience. We will also add a blueprint-callable spline function SetScaleAtSplinePoint which can be used to set the Y and Z scale. The X scale is not used in spline points since this direction follows the spline.
(Side note: Feureau’s example at the beginning of this thread is out-of-date now but it only would have affected the spline point’s up vector. Be aware that internally USplineComponent’s member data SplineCurves.Rotation, which replaced the now-deprecated FSplineRotInfo, is only used to rotate the up vector from its default position. The resulting up vector and the spline point’s tangent are then used to derive the side vector.)
Apologies for the delayed reply!