In TTG CE3 Stage, the “CE3 Standard” layout is a slimmed down version of the standard CE3 thumbnail grid and launches images using Photoswipe. Honestly, we do not intend anyone to use this gallery mode as a primary presentation type. If this is the sort of gallery you want, then you would be best off using TTG CE3 Gallery.
The reason this layout is here is that it is used as a mobile fallback, optionally, for the Full-screen “Flip” Gallery and Galleria slideshow. The layout may be selected as a presentation option in Lightroom with the intent that users should be able to customize the appearance and behavior of their galleries for mobile devices.
To use, in the Color Palette control pane set Page Type as “CE3 Standard”:
In the Appearance control pane, in the Page: Staging control group set Gallery/Embed Style as “Before & After”:
This mode is best used with Lightroom's Web preview sized to mimic a mobile display. For more information on setting up such a workspace, see here or watch our YouTube video on creating a responsive workspace.