In ArcGIS Desktop ArcGlobe or ArcScene, a layer could be displayed vertically "floating without a surface" with a defined “layer offset”.
https://desktop.arcgis.com/en/arcmap/10.6/extensions/3d-analyst/setting-a-raster-layer-s-base-heights-using-a-surface-in-arcglobe.htm
The help added the tip: “To float the layer at an elevation provided by a constant offset, switch the option in step 3 to Floating without a surface and simply provide an offset in the combo box at the bottom of the dialog box.”
This does not seem possible in ArcGIS Pro scene. It is a common requirement to view surfaces as horizontal slices and having the ability to float the layer at specific elevations would be most helpful.
Perhaps I am missing a setting?