This is a script in GDScript (Godot 4.2) that allows you to set a Node3D as the parent of several GPUParticles3D effects which are all one-shot effects. When you call `trigger()` on it, it'll start them all. When they are all finished, it kills the node. Remember to add all your effects as children to this node.

one-shot-effect.gd

class_name SingleEffect extends Node3D

var effects: Array[GPUParticles3D] = []
var effects_completed: int = 0

func _ready():
	# get all the GPUParticles3D nodes under this node
	for child in get_children():
		if child is GPUParticles3D: effects.append(child)

func trigger():
	for effect in effects:
		effect.one_shot = true
		effect.emitting = true
		effect.finished.connect(_on_effect_finished)

func _on_effect_finished():
	effects_completed += 1
	if effects_completed == effects.size():
		queue_free()