Scel not looking at the videos, what you want is a thing at the side that selects an item like the skull in doom?
a solution is to use godot's own system.
1 - create a theme for your UI, the first Control can have this and all children will inherit from it.
2 - create a button style, set the styleboxes to new texture style boxes or flat.
3 - there is an option called focus, here you can create a stylebox with your cursor.
4 - in inspector, set next and previous buttons to navigate between the buttons using the keyboard.
