Basemaps can be added by users with the "Add New" button :

When ArcGIS Earth is closed with a user added basemap, all the information about that basemap is correctly stored in the lastBasemapInfo tag of the ArcGISEarth.laststate file :

But when ArcGIS is opened again, the basemap shown will not be the user added basemap. Instead, it will be switched to Esri Imagery. The user added basemap is not completely lost, because the user can manually reload it from the basemap list :

Is there a way to open ArcGIS Earth with a user added basemap?
Note : there is no problem with all the Esri basemaps. For instance, if I close ArcGIS Earth with the Dark Gray Canvas on, this particular basemap will be the one used next time I open the software.
Thanks!