I have been looking for a 3D scene builder that could be used to design game levels for Gideros, but couldn't find something that fulfill my needs. Blender is far too complex to use, Asset Forge (by KenneyNL) is nice but don't allow naming/tagging objects, so I decided to have a go to writing my own scene editor, in Gideros.
It is very early days, but it is already capable of showing an asset library and position models in 3D space with ease. It lacks almost everything else: opening/saving projects, rotationg and scaling objects, adjusting properties, etc. but I think I am on the right track.
Here is a screenshot, using assets from KayKit on itch.io.