I’ve just put up a new build with some more fixes and improvements.
Besides bug fixes there’s also some UI changes.
New Upgrade Plugin Command.
Upgrading a plugin is now done via a dedicated right click command.

Upgrade plugin will attempt to upgrade a VST 2 to 3 plugin maintaining the plugin state. Replace plugin will now always replace the plugin with a new instance and discard any previous plugin state.
If the plugin doesn’t support upgrading the command will be disabled. If the plugin says it supports upgrading, but really doesn’t you’ll get an error message and the plugin will be left in a failed state.
Note that it appears all (or perhaps most) Arturia plugins fail to upgrade. I’ve reproduced this in Cubase Elements and forwarded relevant details to Arturia and they’re looking into it.
Undo Upgrade Plugin
You can now undo a plugin upgrade. This is particularly useful for plugins that fail to upgrade.
Plugin Properties
You can now right click on a plugin and choose “Properties” to see detailed information about it.

Misc Fixes
I’ve also made a couple of fixes to the VST 3 hosting. There are still known issues which I’m working on but wanted to get the above changes out before investigating further. I’m also in discussion with several plugin developers about other issues and will continue working to get this stable asap.
Stay tuned and thanks everyone for your help with this.
Brad