originally I counted nodes in group in process function, which was very bad.
so maybe somehow I could get access to this static variable from decal in parent node ( Projectile) and use it also for naming.
To make it more clear → Launcher is attached to Camera in Player.scn, it initialize Projectile.scn when attack is executed( this is Raycast3D), if this hits mesh Decal.scn and explosion_scene.scn are initialized and added to collider.