Does anyone know how to get out of KeyNote Sharing ****?

Context and followup: pure Apple Ecosystem (no Dropbox, no OneDrive). File created and located on the MBP in a folder on iCloud Drive. KeyNote file opened in KeyNote and four slides added. Share feature was used to add an external user. Solid internet connection. This resulted in the above user experience. At a much later time, it was possible to make a copy of the KeyNote file. Three of the four new slides recovered. Data loss (one slide) was final result. Fortunately, a photo was taken of the screen when KeyNote/Finder failed, so the lost data could be reconstructed from the photo.

The sync failure appears to be an edge effect or race condition triggered when adding external user using the Share feature in KeyNote. It lost sync with itself. It was unexpected user experience to have KeyNote do nothing (no modal, no response at all) when using the open file action. It was unexpected user experience to have Finder unable to duplicate the file with a hung downloading modal box and/or no response at all when clicking on the file.