Because of each beta apparently being a stand-alone install I have 9 copies of scrivener showing on my “apps and features” list. Does anyone know if the older ones can be safely uninstalled? I have a bad feeling about trying it

Yes, they can be safely uninstalled.

They may be safely uninstalled. With each new beta, the existing beta should tell you there’s an update, and the internal updater does work. It doesn’t change the version listed in “Programs and Features,” which can be confusing.