You can nest Borders, but make sure settings are proper (padding, aligning).
Make sure You have put it inside (hierarchy window), not just put them on same place.
But border can hold only one element, so You need to put Canvas or other nesting element inside.
Several elements on same level of hierarchy will be sorted in order - top in list = bottom in zIndex.
Vertical box stacking elements vertically, that’s what title says. You can’t freely move content inside, use CanvasPanel for that.