FB17945555 generated.
Thank you for the prompt reply. I was looking to explore what would happen with a clear background in an effort to make my control panel less obtrusive. I'm not sure I have an application for it yet other than exploring design options.
HOWEVER, perhaps the compiler error could be downgraded to a compiler warning. In other cases where functionality is missing (I'm looking at screenshots :( ) and their code is 1. not generated or 2. invocations generate no warnings and fail silently.
Proposal: Replace the error with a warning and simply ignore the use of .glassEffect() on visionOS. That should save developers a lot of unnecessary #if coding at the risk of their visionOS UI breaking in the future should .glassEffect() be implemented in visionOS and the warnings disappear.