When editing a scene, if one adds new 3d nodes, in this case sprite3ds, (i am duplicating the same that is alredy shown), it does not show on the debug launch, only in the editor.

This behaviour seens to ocour in some other aspects.

Changing the Mesh of a MeshInstance will either:
If deleted and change, show nothing

If just changed, contining showing the previous one.

CLosing and lanching again the debug instance fix all. but this makes unable to live work on prototiping.

Is this a bug, documented/reported?

I don't know if it's a known bug.

What platform (or platforms) is the export?

Can you create a Minimal Reproduction Project?

Also, please state the exact Godot version.