i would like to customize the tilemap collision outlines, since providing a collision map of the same resolution is creating an unwanted gap between two slope tiles meant to be placed together (circled in red.) is there something i can do to make this notch disappear and make it a triangle instead?
You can put an extra ‘guide’ pixel in to trick the collision outlines into working how you want.
You can do this ether by creating a collision mask with the extra pixel present or if you’re super-lazy like me, put a very low opacity pixel onto the actual image. Kind of a fudge but it should work in this case.