I am trying to edit sprites at runtime (using a sprite to store a large map), I know the sprites can be resized and from what I can tell the limit is 512 pixels in dimension?

I managed to draw to the sprite using set_draw_target() and then pset to draw the pixels I want, but I can't figure out how to then read the pixels! The guide mentions sset and sget which I know from pico8 but I can't make them work for some reason, I figured maybe I need to return the sprite as a user data with get_sprite but then sget doesn't seem to be a function of user data and can't find anywhere that explains how to use sget and sset.

Also I know the sprites will reset when the game is run so how would I then overwrite the sprite with the edited version so I can save the generated map?