You don't need .3ds to build paths, you can place footers next to each other to make a path. Sure, it doesn't look that good, but better than nothing.
This heartline thing, it would be a good idea to place the heartline, not the track, and build the track around it. For example, you want to build an inline twist, you draw a straight line for the heartline, and the track forms underneath it, like the heartline appears above the track now. Then you bank the track to go through 360 degrees, and the editor moves the track to keep to the heartline you made.
Just a thought but would make it much easier
This heartline thing, it would be a good idea to place the heartline, not the track, and build the track around it. For example, you want to build an inline twist, you draw a straight line for the heartline, and the track forms underneath it, like the heartline appears above the track now. Then you bank the track to go through 360 degrees, and the editor moves the track to keep to the heartline you made.
Just a thought but would make it much easier