Pro Tools cannot find (all) my aax plugins.

[JesperT]

Pro Tools 2018.12.0 cannot find (all) my aax plugins.

I created a folder called "Sound Libraries" on Drive D:

In this folder I have installed "Structure" and "Velvet"
They are located in D:\Sound Libraries\Digidesign\AIR Content\Structure
....and in D:\Sound Libraries\Digidesign\AIR Content\Velvet

In the same directory are: D:\Sound Libraries\Air Music Technologies\Xpand2 (and Factory Content)

Pro Tools is searhing for Sound Libraries in D: Sound Libraries

However, Pro Tools only shows Xpand2 in the instrument list, while Velvet and Structure are not found.
I guess the missing plugins are installed to C:\Program Files\Common Files\Avid\Audio\Plug-Ins
...but how do I tell Pro Tools where to look for them?

And when Pro Tools eventually finds them, how do I tell the plugins, where the sound libraries are?

Thank you
Jesper