When I made my current game in Godot it has a ground mapping feature that let me draw onto my scene all areas that were a collision object.
For me I use this block out my objects paths, rocks, wall, houses etc that are just part of the background image- so that I can interact with them- block passage, block placement of tower, deletion of colliders.
In defold I believe the only similar thing is tilemapping collisions or creating objects for collisions?
So do to the same thing I would add a collission tileset over those areas?