I can't find the instructions that explain how to parity sync in 6.0 beta 4 -- I'm no longer given the option on the Home screen.  Please advise/link.

Parity sync or parity check?  Parity sync starts automatically when creating a new config and starting the array. Parity check verifies parity. If you don't have a parity check option then one of your disks may have a red ball meaning it has been dropped from the array and is being simulated. When in this mode a parity check isn't possible and the option is not available.

Ah, you are correct -- my brand new 2nd drive has turned red.  It is a new drive, passed all benchmark checks, etc.  I switched to beta 4 because my last 2nd disk also went red, then turned out to be fine.  I guess the problem could be with my other hardware -- cabling, etc -- but that doesn't explain why I am no longer allowed to access the server due to permissions.

There is a newperms script you need to run if migrating from 4.7. You need to pull a smart report from the red balled disk to help determine if the drive is failing or you have a bad or loose cable.