In ArcMap/ArcScene exists an Toolbox-option under the 3D-Analyst extension to export/convert a 3D-Scene (created in ArcScene) to a "cityengine Webscene" in 3ws-fileformat (3D Analyst Tools / Cityengine / export to 3d Webscene).
This file can be viewed using the Cityengine webviewer-html and can be easily excessed via own Webserver or even offline, which is very usefull to share smal 3D-scenes, alternativ to Arcgis-Online Webscenes (since AGOL 3D-Scenes still lacks some funktionality, espacially offline use).
However, in Arcgis-Pro is no option or Toolbox implemented yet, to exort a 3D-Scene created in APro into this 3ws- cityengine-Webscene format.
Currently we need to rebuild a 3D-scene in Arcscene (or Cityengine) to get the Cityengine Webscene Format.
(Unfortunatly easy exchange of 3D-Scenes between Arcscene/Arcgis-Pro/Cityengine is not possible, at least not "backwards" to ArcScene)
So please implement the option to export 3D-scenes from Apro to cityengine Webscenes (3ws) also in Arcgis-Pro (3D-Analyst extension).