The Add Preset gallery is deprecated and will be removed in ArcGIS Pro 3.0.
There should be no major impact to customer workflows. Preset layers can continue to be used in ArcGIS Pro 2.x, and they remain compatible in online maps.
In ArcGIS Pro 3.0, users can add a Subtype Group Layer or an elevation/ground layer through the Add Data menu. Maps with existing layers created from preset types can be used as-is in ArcGIS Pro 3.0 without modifying the layers’ symbology. Users who need to modify preset layer symbology will be presented an option to Convert the layer(s) in the ArcGIS Pro 3.0 Symbology pane. Converting allows users to modify symbology, as the layers will contain a regular simple renderer or regular unique value renderer after conversion.