I'm also new to godot and ran into a similar problem with something I'm working on. What I did to solve this was to create a higher level scene that uses an instance of both the paddle and the ball. (right next to the + icon to create a new scene there is a chain icon to add an instance of another scene, or you can do through code.)
then you can access the properties of those instance with the $
var paddle_pos = $paddle.get_position()
an example of adding scenes in code:
extends Node2D
var paddle = load("res://Scenes/player.tscn")
var balls = load("res://Scenes/ball.tscn")
func _ready():
var player = paddle.instance()
var ball = balls.instance()
add_child( player )
add_child( ball )
#NOTE: no $ sign when using variable name
var player_pos = player.get_position()
LIke I said, I'm new to this too, but that's something like what I did and worked for me.
Garrett