On the Melda thing, the documentation on Ozone says it only scans one folder level deep on the VST scan.  So it does the folder you enter and it's children, but not their children.  My Melda plugins are two levels deep, MeldaProduction\Tools MeldaProduction\Stereo etc.  I think if you want those in Ozone you'd need to add the MeldaProduction folder to the Ozone scan list. 
 
Update: I added the MeldaProduction folder to my Ozone 7 VST paths and on a rescan it did pick them up and they seem to work.  Though to be honest I hadn't actually noticed they weren't in the list before, I think I may have too many plugins.

This is from iZotope Customer Care
"Thank you for reaching out! Unfortunately WAVES plugins are not supported for use with Ozone 7. I apologize for any inconvenience here. This is due to the limitations of Waves Waveshell with our software."
 
If you see this video https://youtu.be/Lp1RG-vZtGA  You will see in the comments section:
"I am using Mac, which means I can install "AU" versions of the plug-ins. Ozone 6 will recognize the Waves plug-ins if you have installed these versions."

olemon
O7 picked up some Cakewalk plugins like the CA-2A, the IK Multimedia stuff, the Nomad Factory BT's, the Blue Cat free pack, as well as some other freebies like the Slick EQ from TDR.  Based on that and your input, it appears O7 doesn't play well with Waves and VST3's.
 
Dang-nabbit.

OZ 7 pickups some Cakewalk plugs but it will give you an error message if you try to use them.  I saw this with Nomad.  They are tied to Sonar.

olemon
And here I was hoping to be able to use O7 like the T-RackS suite, but with my plugins of choice.  Had I known, had I read the fine print, I probably would not have gone for that O6/O7 deal, since I moved away from O5 as a mastering option.
 
Hopefully this thread will help someone avoid the same erroneous thinking.

I know, an absolute disappointment in Ozone 6, and then again in Ozone 7.  Like I said, a deal breaker.

msorrels
On the Melda thing, the documentation on Ozone says it only scans one folder level deep on the VST scan.  

Thanks, I'd missed that.
 
Unfortunately, that didn't seem to help me out. My favorite Melda mastering plugins are in c:\program files\cakewalk\vstplugins\Meldaproduction\EQ, but adding it to the folder list didn't make them show up. 
 
Oddly, it does find my FabFilter stuff even though it's not even under vstplugins (\program files\cakewalk\fabfilter) and not explicitly included in the folder list. Same for the other iZotope plugins, they're not under vstplugins, either but O7 found them. At first I though it was smart enough to scan horizontally, but then it didn't find my ValhallaDSP plugins, which also aren't under vstplugins. Can't seem to figure out the pattern of why it gets some and not others.
 
[EDIT]
My mistake. The Melda and ValhallaDSP stuff is there now, lumped under the "Unknown" category along with Boost11, Z3ta+ and Zebrify. 
 
BTW, you can actually insert another instance of Ozone 7 within Ozone 7 standalone. Now I can get REALLY loud masters!
 
J/K, but it is cool that you can have multiple Dynamics modules in one instance by inserting the standalone version as if it were a "third-party" plugin. Too bad you can't do that with the plugin version of Ozone. As it is, you can only have one instance of each module.
 

Yeah all the Melda stuff is in Unknown.  I think it's pulling that category from some internal VST field.  All my shell2vst Waves plugins end up getting their own folders in Ozone 7.  So I have a folder called "C1" with the Waves C1 plugins (stereo/mono/sidechain/etc).  And so on.  But tons of my plugins are stuffed into Unknown.
 

bitflipper
I had mixed feelings about the standalone application. At first I was excited about it but as I built up a practice project out of random wave files I gradually realized that my old process of mastering within a separate SONAR project gave me greater flexibility.
 
So it's back to using Ozone only as a hosted plugin. Very, very satisfied with it in that context. (I, too, had been moving away from Ozone for the past few years.)

+1 And you can use your existing plugins in your DAW Mastering Chain. I also have Ozone 7 Advance, and the standalone is good for a quick or rough mastering project (my opinion), but the limitations of the number of modules that can be used in one project, led me back to mastering in my DAW. Definitely did not take away the value or confidence in the purchase of Ozone 7. And no limitations when Mastering in DAW. Great bang for the buck and well worth it, once you figure out an acceptable workflow (matter of personal preference of course).