Qt Designer making dynamic GUIs

I'm trying to figure out a way of using Qt Designer to make a dynamic GUI. For example, let's say I have a main window with a horizontal layout. I have a push button on one side and an empty area on the other. When I click the button the empty area will be filled with a widget that I've made in Qt Designer. When the button is pressed again the widget will be replaced with another widget that I've made in Qt Designer. Would I have to go about making all my widgets, to fill the empty area, custom widgets?

I've tried setting the parent to the empty are, but on the second change I get this

QLayout: Attempting to add QLayout "" to QWidget "t2", which already has a layout

So then I tried deleting the layout but still see the old widget underneath the new one and the layout is now messed up.

help please