Use the Layer Showcase app template to provide app users a simple and interactive way to browse a gallery of 2D and 3D layers and then use those layers in maps and scenes. App users can explore layer-based content, viewing it on a map or globe. They also have the option of creating a map based on the layers.
The vast majority of your work should go into styling and documenting the layer items. You can then share the layers with a group and use the Layer Showcase app to deliver content.
To see the options available for this template, search your ArcGIS Enterprise portal using the app template name and open the app template item's detail page.
This app requires a group that contains the layer items you want to showcase.