The link in the first post was a cap file for Construct 1. It wouldn't be useful for C2 or C3.
Have you tried doing the logic for the falling sand yourself? It's pretty simple. Move down if the space below the grain is empty. Or if that isn't empty try moving down left or down right if those spaces are empty.
You have options with how to do it. Sprites, tilemap, or drawing canvas are options.
If you do it with events you'd want to only use system compare and else's under a loop to avoid as much picking overhead as possible.