You're right, the official process does require a reinstall - I'm hopeful that the next update will be a combo though, which you're probably aware would mean you'd only need to reinstall 10.11 Beta 1 from the USB drive and then update straight to Beta 7 - it's likely that we'll only have to wait 2 days to see...
Anyway, the process to manually create the RecoveryHD partition requires you download the El Capitan Installer again (if it isn't still sitting in your Applications folder from before) - 2nd time around normally requires you to hold alt/option while you click the Purchases tab...
Happily, from there there's a script that cuts out all the intricate stuff, which can be downloaded from here: https://dl.dropboxusercontent.com/u/13872235/Musings/Recovery%20Partition%20Creator%203.8.zip
@Max108 thanks for your response. I'm one of those techs who saves everything as he works, so I have the latest El Capitan Beta installer app.
I downloaded the El Capitan Beta Installer app to /Applications on the MacBook Air test machine.
Then I downloaded the AppleScript app and ran it, and I skipped past the error:
You are not running a compatible version of OS X
I hit OK and selected the target disk Macintosh HD > OK. The next dialog box I got is:
We will now check your drive for errors. You can skip this but it is not recommended
I hit OK and gave it less than a minute (because SSD), then got:
We are about to start the recovery creation process. Click OK to continue and choose the OS version you are going to install when prompted.
I hit OK and after a few seconds I got this dialog:
Choose OS Installer Version [10.7 or 10.8] [10.9]
Since we are installing 10.11, I took a chance and chose 10.9. Got Creating Recovery artition. This is going to take a bit. with an Abort Recovery Partition button that for obvious reasons I did not hit.
About a minute later I got a Your recovery partition has successfully been created. Reboot and hold the command and r keys to boot to the recovery partition. I hit OK and then quickly ran diskutil list to confirm Recovery HD is there (yay!). I ran diskutil cs list and got the same No CoreStorage logical volume groups found which I sort of expected.
I rebooted holding COMMAND-R and gave it a couple seconds to boot. BAM! There we go, El Capitan Beta recovery partition!
This is awesome, hopefully this thread with all the details will help the next person who has this problem.
PS, do we know who the developer of the AppleScript app is? I'd like to provide some helpful feedback, and ether-beer if possible.
Glad it worked - I did it manually once with Mavericks (pkgutil was heavily involved I remember) and knew that this script worked with Yosemite, so I was pretty sure that the same process would be continuing to hold for subsequent versions of OS X - good to have it confirmed though. I had the sense from reading your question that you'd appreciate the context of the warnings the script gave (I ran it just shy of the final step myself) and push on anyway, but the step-by-step you posted will be very reassuring to many others - thanks.
Who wrote the AppleScript? This guy: http://musings.silvertooth.us/about-me/