There are some multi-track splines, but not 100-track splines. They are also come with some caveats too and I think are now obsolete assets, but still exist and work due to compatibility reasons. Off the top of my head this is what I recall about them. It's been sometimes since I've used them myself, and if I've run across them, I've replaced them with single track splines.
They are not track in the sense of track splines. They are now classified as bridges.
Being bridges, you cannot form junctions with them and will need to use a matching single-track to create junctions. You also can't use the replace asset function if you decide later to replace the chosen asset with another. The Replace asset function does not work with industries, stations included, bridges, and MO-crossing objects such as road intersections, and fixed-track assets.
These assets also don't bend well and sometimes have odd segments to them with the ballast breaking oddly at the segment edges.
These multi-track splines also have a performance issue as well due to how they're constructed, and you'll have stuttering and pauses worse than what's already there in TS10 and TS12.
