(Done entirely from scratch, so lacks some of the problems I left you in the static example, as well as letting me play with combo effects more.)
Plain / Wall-shade-area (Red) / + Wall-shade directions / Wall-shade-filled
Plain / Ramp-shade-area (Blue) / + Ramp-shade directions / Ramp-shade-filled
Plain / Both shade-areas (Red+Blue) / Both shade-filled (overlap*) / ...without outline
... / Both shade-area / Both shade-filled (diagonally abutting**) / ...without outline
Plain / Combined-shade-area (Magenta) / + Combined-shade directions / Combined-shade-filled*** / ...without outline
* - double-density in the corner
** - slight gap left due to not fully dealing with the feathering issues during editing
*** - maximised at the corner, which therefore wouldn't match further afield along the edges than in this example (I seem to have lost the square-cornered-shading frame I thought I put after that in that sequence, I probably just didn't make that last layer visible again before exporting it all to GIF and bringing it away from that machine for posting)
I could have upscaled it (before or after annotation), but I'm sure you can easily zoom in with a screen-pinch or Ctrl+ command for a closer look.
NB: The shading is just straight darkening (petering off to half a tile away from the vertical edge(s), give or take ramp-slice adjustment), not the hue-biased illuminated shading that Tarn clearly is implementing in the source screenshot. Nor did I (in this example) take the shading boundary beyond the tile boundaries involved (which I'm not sure is currently being done, but perhaps ought to be, e.g. on the diagonal flat tile next out from a convex corner-ramp).