Well, I think the carve crosser is completely fleshed out. No details yet, but here is a shot of what you can do with it.
The first image shows basic useage through a raised section, cutting the raised section into canyons. The second image shows a three corner trick, turning two diagonal raised tiles into three adjacent mountain peaks. The third image shows that I forgot you could use 0 and level 1 stuff on the base level, so this is what it does if you carve the ground level. And the fourth image shows what a few piles of mountain with carvings looks like in front of each other. Nothing special.
So just to be clear, I was going to do a different chasm appearance than what is shown in image 3. I wanted a very sudden chasm which goes out of sight range almost instantly. So if I get around to that soon, that chasm will be in addition to the carving of the ground layer with the carve tool. Take that as a bonus. True chasm tiles will be corner-based, not crossing-based.
So about the carved canyons through raised terrain: They aren't flat or walkable by any means, but I do have them currently set to full walk and pathtype A. This lets me test the shadows and go wherever I want to for debugging purposes. I do not intend to make all the canyons and nooks and crannies walkable. They're just for scene texture. That being said, I do have plans for a number of walkable groups which do make use of the nooks and crannies. It's just that the amount of walkable room in these canyons isn't enough to supply a flat space for any monsters. They'll simply get hung up in the cracks. So when I do the groups for the carved areas, what you'll see is areas with obvious walkable space. I'll make room for various sizes of creatures to walk through by carving manually even further, and also taking back some of the mountain space above by disallowing higher Z-level characters from walking on them. It should work out well in the end.
You can see by the next image, I kid you not, you can carve 'til you are crazy from carving.