There is an other option: in engrave mode there is a property for ornaments, ‘Slur-relative position’ which if you set to Inside the ornament will be place inside the octave line. (Slurs, tuplets and octave lines are processed together to decide their relative ordering, so the property really controls whether the ornament goes inside or outside of those three items).
We would indeed like to improve/generalise the relative ordering of objects in the future, but it’s a reasonably complex problem so will need some time to implement, and it’s not on the short term plans.