@Stefan1507
You can do that even with 3dsimed
1. Find all the 1WALL meshes or the 1meshes you want not to be physical anymore via the Display - object filter
2. Copy them to a new tab inside 3dsimed with crtl+A copy
3. Rename all the 1WALL meshes from step 1 to WALL in order to stop being physical via the Tools - object rename tool
4. Export to fbx, load it to kseditor and save the track as kn5
5. Go to the new tab you created at step 2 and export the whole scene to fbx 6.0
6. Find the fbx ini file with the same name as the one you set during the export at the previous step.
7. Open the file with notepad ++ and find and replace all VISIBLE=1 to VISIBLE=0 and all RENDERABLE=1 to RENDERABLE=0 and save the file
8. Load the fbx from step 5 to kseditor and save it as walls.kn5
9. Add the walls.kn5 to models.ini
10. Test
11. Enjoy
Your best option though is to ask @VehEth to update the track because in order to post the fix you need his permission, else you have to keep this only for yourself