"almost ready to go". Couldn't you encode this in collada directly? It's very likely but it's my understanding that AssImp won't load the data so I found another way. Edit. As a side note, make sure you write the custom props in the correct place. It is possible to put custom props pretty much everywhere. In nodes and materials for sure. I think meshes also have a custom prop capability but I'm not sure. Sure there are other places where custom props could be used but I'm not all that good with Blender. Just keep it as simple and practical as possible at the beginning. When I did a simple 3D level editor(simple as in 1 weeks work) I made sure It was a completely separate entity to my game. Therefore, the only thing I needed to do was to decide how I was going to store the data, so I could parse it accordingly when my game loads the level. It did however use alot of the code from my game, most notably the render and input code, with modifications to suit the editor; Because I had such a short amount of time, I decided to limit the artists abilities to just translate,scale and rotate objects. I also decided to leave out the ability to add textures in the editor. I believe as a starting point, this is what you should aim to do. You would have to make a decision as to whether or not you want to