I copied pluginmanager.xml to cubase 9 from 8.5, but I don´t see my collections anywhere?
Sounds like you’re in the similar place to where I was yesterday, when I opened an old project only for C9 to fail to find GA One. I solved it by copying its files from the VST3 folder in ‘Program Files\Cubase 7.5’ to the VST3 folder in ‘Program Files\Common Files’.
So, the question is: where are the plug-ins you are looking for? Are they in a common area or somewhere where only a particular version will find them. If they are VST2, then are your paths set in Plug-in Manager?
Also, don’t forget that 32-bit plug-ins no longer work.
Happy hunting, C 
I see all the plugins that’s not the problem. But I don’t see my own plugin collection which I created in 8.5. In other words I made folders and organized plugins the way I wanted.
Solved the problem copying also the plugin.xml file. So for me it was copying pluginmanager and plugin.xml files to get it to work.
That’s good to know. I wonder what it would take to get an option to migrate the settings as part of the original installation? I’m losing count of how often this sort of question keeps coming up…
I wonder what it would take to get an option to migrate the settings as part of the original installation?
Well settings do attempt to migrate on installation already, they just fail quite often…some permissions things with certain Windows systems I guess.
But Steinberg have provided another way that no-one seems to know about - You can save a Profile in old version and import it with Profile Manager in new version.
This is arguably more flexible than a default “on installation” migration as you can even have different sets of prefs for different users or scenarios and you can freely swap profiles between computers/versions at any time.
Brilliant! How long’s that been there? Nice one, Grim
Fairly new…maybe only appeared with 8.5.