Hm.. You're actually right. I guess I'm overcomplicating things again, as always.
I guess I'll just instance the inventory node within the player node, without using any specific code for it.
One more thing though... I created a menu upon pausing the game. Right now I manually put it in every scene where pausing is possible. It is basically a small overlaying menu, that also makes the current scene darker while active.
If I am to keep it as an overlay, where do you recommend placing it? In the Player scene just like the inventory?