UPDATE: it reconciles only UV changes from Blender, if you change the mesh, nothing happens.
Anyway, a new feature is schedule to release which is export from Vertex Studio back to OBJ or GLTF (so what you paint in Vertex Studio can leave Godot itself). Then you can open the OBJ/GLTF in Blender, update the mesh and reimport back into Godot. More info: https://splitpainter.itch.io/vertex-studio/devlog/1630666/export-objgltf-terrain...