In a sketch, Solidworks has this amazing way of letting you trim/extend any projected entities (even complex spline) without loosing the projection constraint.
It also make the Trimming/Extension dynamic, which means it can move and adapt if you change your construction flow.
Right now, with Fusion 360, I seem to only be able to project an entity, then remove the projection constraint, then trim the part I want (extend is not really an option at all) and then add a fixed constraint...however this is definitely not dynamic and when you remove the projection constraint of a complex spline it usually makes it overly complex...
