When isLayoutMarginsRelativeArrangement
property is true, the stack view will layout its arranged views relative to its layout margins.
stackView.layoutMargins = UIEdgeInsets(top: 0, left: 20, bottom: 0, right: 20)
stackView.isLayoutMarginsRelativeArrangement = true
But it affects all arranged views inside to the stack view. If you want this padding for only one arranged view, you need to use nested UIStackView