www.wysiwygwebbuilder.com

In flex container, the image is set as a background in parallax mode. How do I change the background image to another one when I click on a button?
Or how to set parallax mode in Styles Manager?

You can update the background image via JavaScript:
https://www.w3schools.com/jsref/prop_st ... dimage.asp

Parallax is not an HTML feature (it a script) so it cannot be set via Styles.