Use the Explode Command - that will detach the dependency on the lines and make them stand alone 3D lines - that is the only way currently to do this as the Sidelope recreates the lines when it refreshes which means that lines that were offset from the lines in the sidelsope which have dependency on the sideslope lines cannot exist.
So create the Sideslope, when you are happy with it, if you know you will never change it again then you can create lines from the lines of the sideslope. If you think you may change something then Explode the sideslope object to create the linework and then they will remain after a change.
The Sideslope object can be found at the start of the source line - there are two things there - the Sideslope Template and the Sideslope Object - it is the Sideslope Object that you want to select and then explode.
Anything that is created from a sideslope object is placed in the "container" of the database with the sidelsope and so are directly affected by the changes to the sideslope object.
Alan