“””””” perhaps the sketch tool can be made to automatically connect lines existing curves to newly drawn ones ?”””””

Yes! The sketch tool makes such beautiful curves but connecting abilities are manual.

If it could be made to have an “endpoint snap” toggle that would keep tangency to curves endpoint snapped onto then continue with its normal behavior, it would be a MONSTER tool!!!

The auto blending/connecting command doesn't exist. One was created that connects “points” within given tolerances. Maybe someone can look at that to see if it can be made to do “endpoints” instead, then do a polylime connection, or a blend….