Layout mode greyed out

Godot Version

v4.2.2.stable

Question

Just starting with Godot. If I create a Control node, be it empty or if I add any content, I can’t change it’s Layout Mode anyhow. It obviously has no parents to prevent it. What do I do wrong?
image

It needs to be the child of a control to activate the layout mode.
Unfortunately I was unable to find any documentation on this property so you will likely have to find some tutorials to figure it out.