Custom ScrollBox scaling

I have a Custom User Widget, which has a scrollbox inside of it. Inside the scrollbox is even more custom widgets.
I want to have different sizes of these “ScrollboxWidgets”, but use the same widget, as the code behind is the same.

In my parent UI, I want to be able to define the size of the widget, but it seems the widget’s size is always determined by the size of the widget inside the widget.

If I make the size in the parent UI too small, sometimes the scrollbox doesn’t work, if there are too many items in it, cause the size of the widget (in the widget blueprint) is larger than the size in the parent UI.

Is there an easy fix for this problem? I tried wrapping them in a ScaleBox with no positive result.