Pragtikal is pretty cool. Mine leverages Lite which is actually all similar. The basis of pragrical and lite are rendering using sdl or other backends. Ive changed mine (in dim) to use the sokol framework.
This framework has 2d, 3d, audio, http fetch and more - this is why I converted lite to use this.
The process to do this for almost any target framework is pretty simple (in lite) but Im not sure about how that works with Pragtikal. It might have tighter bindings (dunno).
My 3d rendering utilizes a luajit based utils set (its in dim) to render basic 3D scenes. Dim’s version is changing fast (there is binning, shader and material management and various other new features recently added).
So to summarize to be able to extend pragitkal youd need:
- Some sort of 3d/2d rendering framework for the render features you need.
- A data exchange mechanism (for in/out of the defold data sets)
- If you want to use IPC (esp across platforms) Id recommend something like luv (I use this for bg procs and such).
- Youd need to build a bunch of plugins for the asset viewing or manipulation.
Not sure why you’d keep the Defold editor? If you want to make a level editor or world editor, then thats kind of a different type of application? You could leverage many of the great open source level editors out there and youd probably get 90% of what you need?
There are some people working with tools like TrenchBroom and Defold already - maybe this might be useful?
My original thinking on this topic was completely replacing the Defold editor with something more extensible and flexible. For me, I currently have with dim 
But I want to be clear, this is not yet “rigged” to use Defold, but it would be fairly trivial to do so (Ie setup a bob plugin and some project/script/asset plugins). This is primarily used for my own works atm - and I wouldnt recommend it unless you are very familiar with luajit.