I added a PR geared towards this functionality if you think it is useful (Added a new mode of operation for flattening without regard for resou… by cabadam · Pull Request #3 · Kayser1444/CoI_AutoTerrainDesignations)

When I set the scanning filter to rock, the scan returned "No minable designations found" and Create Designations did nothing. It feels like something may be intentionally excluding rock? The description on 'Scanning filter' even says:
None = useful products first, then debris, then dirt

Which also suggests Rock isn't considered useful for anything

You mentioned debris, which I don't think this is. I've circled an example of what I hoped would be marked:

Is there a way to use this to level all terrain within the control tower's area to a particular elevation? This sort of sounds like Flat "bottom" terrain designation | COI Hub but I'm not sure it has quite the same purposes.

So the goal here isn't about getting a particular resource out, but making room for the next place on my …