I would love the ability to configure pop-up windows with text/pictures and/or maps in the regular Story-map's building interface.
In specifics - in my viewing the function could be smilar to the one available in the Experience Builder. Ie. an ability to configure a button to led to a new window within the same Story-map. This would be very helpful in keeping the main Story map "clean" and give the reader oppertunity to deepen it's knowledge in certain fields if needed or wanted.
Edit: Attached is two screenshots from an Experience builder app. Picture 1 shows a button inside the red marking. Pressing the button leds to the pop-up window in picture 2 - in this case a picture and some information.