The Hero Scroll Stack is a section that contains multiple hero images. As the user scrolls down the page, the images appear one by one in a horizontal scrolling effect.
Hero Scroll Stack section contains multiple Hero media items. You can click Add block to add new items.

Media type: You can add either an image or a video as media.
Image: Upload the main image displayed on desktop devices.
Mobile image: Upload a separate image optimized for mobile devices. If no mobile image is selected, the desktop image will be used automatically.
Media overlay opacity: Adjust the overlay darkness applied on top of the media.
Appearance Settings: select the color scheme for the content displayed on the hero section. You can choose a preset color scheme or customize it from: Edit scheme

The Content block works as a container for organizing the content displayed on top of the Hero Media section.
Instead of adding text and buttons directly to the Hero Media section, you can add a Content block, then add multiple child blocks inside it to build your hero banner layout.
The available child blocks include:
Countdown Timer: Box
Group Button
Heading
Label
Spacer
Text
You can reorder these blocks by dragging and dropping them in the Theme Editor.

The child blocks must be added under the Content block