I tried it, but it still hickup.... Maybe I did wrong, but I tried so many times.
The code I use is
(in the player script)
var projectile = preload("res://GameObjects/Entities/placeholdershoot.tscn")
onready var playershoots = gettree().getroot().getnode("World/Player_shoots")
the input function call the shoot function whenever mouse1 is pressed
playershoots.addchildbelownode(playershoots, projectile.instance(), true) ( I also tries with playershoots.add_child(projectile.instance()))
and also, I need to instanciate every time I shoot, because otherwise it will spawn only one at time.