@Miroslav , welcome to the community and thanks for your question.
The vertical vs horizontal settings is really just setting which way the widget should scroll if there is more content than space for it.
But I have two other suggestions to force vertical arrangement.
#1 - GroupBox2 if you truly only have buttons, I would use a ButtonBar widget (relative, autoscroll=true). The buttons have a width 0f 100% and only a top and bottom margin. ButtonBar is only useful if you don’t need multiple buttons active at the same time.
#2 - GroupBox3: similar to @Simon_Stoll 's suggestion, use a groupbox (text removed) to encapsulate all your buttons(widgets). Optionally use the same 100% width setting for the buttons. You can see below only the numeric input is set to a percentage since it moves with the width of the GroupBox.
