Sections really aren't 3D windows.
They are analytical views tied to the model data.
If you ARE working in section, any linework you add is treated as any drafting in the floor plan would be. Trimmable slimmable.
You CAN make a DRAWING from a section. This explodes the 3D objects and elements into their composite lines and fills. In this case, it ALL becomes UNLINKED drafting.
If you actually need to draw in an internal engine 3D view, a cheapandnasty way is to export the view as vector lines and paste them into an independant detail. boring drafting, yet again.
Dwight Atkinson