You can do it with Mesh and SEO. Here's how:
1. Create polylines that mark the contour of the ramp. Duplicate them and then create two separate meshes. The first part should end a little before the ramp crosses itself for the second time so you wouldn't get any errors about intersections etc.
2. Magic wand the two meshes inside the contours. This makes sure that you have a minimal number of points on the mesh.
3. Offset one of the polylines to create a centerline for the ramp.
4. Open the Element Information panel (Window/Palettes/Element Information).
5. Select the centerline and note its length from the EI panel.
6. Split the centerline into separate parts (Explode into current view) and then starting from either end of the ramp select one part of the exploded polyline and check its length from the EI panel. With a few simple math equations (think percentages) you should be able to get the needed amount of elevation for that specific point on the mesh.
7. Elevate the meshpoints according to your calculations. Rinse and repeat.
8. When done Elevate a copy of the meshes downward as much as needed and then SEO the meshes separately and place the operators on a hidden layer.
9. Voila!
Hope this helps
Running ArchiCAD 23 INT.