Here’s how you define collision groups in your tilesource. First you select your tileset as the collision file (or you can use any image with transparency as long as the tiles are at the same spot as what they are supposed to represent in terms of collision), then you can select and paint the groups into your tiles. So in this image I have the ground as default collision group and water as water collision group.
Then on the GO you added your tilemap to you create a collisionobject and set its shape to the tilesource. You will also want to make sure you set the mask to what you need, the group will be set by what you have in the tilesource.
Updated with tilemap
TopDownBox2d.zip (5.4 KB)
You can of course use layers too if you want to have some collision groups not associated with tile images but want to be able to paint freely you would use a transparent tile along with a solid (or whatever shape) collision image pair. There are other solutions too.