I have saved the .blend (the scene originally has the object seen in the pic below) in the project folder and Godot imported it successfully. I can see the asset as meshes in the instance scene and in the scene browser.
The thing is that I want to be able to instance individual objects from this import (like Suzanne). I am looking for how to do this in a GDscript and doing it in the editor, since I need them as separate objects, instancing this import in the scene just instance all the meshes as single asset in my scene
You can instance individual meshes by opening the .blend Import > Advanced > Meshes and for each mesh enable Save to File, give each a name and reimport, create a new scene with a MeshInstance3D that points to the mesh file and save as .tscn which you can then instance. Changes to .blend file will reflect to those individual mesh files.