build_height_table writes 21 entries here each frame, from $E301, with $A0 left as a sentinel after the last. Each is the screen row that road slice is drawn at.

These drive the per-frame sky and ground colour boundary in ds_attributes. $E34B is the previous frame's rounded minimum height, $E34C the delta from it to this frame's, always a multiple of 8, and $E34D that delta a frame later.

build_height_table writes $E34B and $E34C by running the height table pointer off the end of the table at CDD1, so neither shows up in a search for their addresses. ds_attributes reads $E34D to decide whether to move the boundary and $E34C for how far to move it next frame.