Over the last few months, especially thanks to 
FoozleCC, I've made good progress on a plugin that adds a real-time 3D editor directly within Construct 3. It allows you to move, scale, rotate and edit your 3D shapes inside a 3D perspective without requiring you to leave the Construct editor.
It is still in development and multiple features are still WIP, however it's already great for editing 3D levels or worlds with ease.
You are only required to install the c3addon – no other software!
https://mountdev.itch.io/3deditor