Which you need to do from time to time, for several purposes.
1. In the 3D window, activate the Marquee tool, and select the flat (4th) geometry method. Draw a marquee around what you want to copy.
2. Copy (Cmd+C). Make sure you have 'Edges' and 'Hatching lines' (if the fills are on). Check the 'Remove Redundant Lines' box. OK. Wait. Some drawings take longer. Fills take a while.
3. Go to appropriate window and paste. Paste to 'Original Location', always. Work copied this way comes in as all lines, on the Archicad layer. There are no arcs and no fills.
4. Change the layer of the lines if necessary. If they're going in the plan, it's necessary. If they're going to a dedicated window, such as a perspective, the Archicad layer is OK.
Drawings which use this technique:
Perspective
Axonometric
Roof Plan