I managed to create a Global Theme and to upload to https://store.kde.org.
In this way, on a brand new system, I can go to System Settings, Global Theme, Get New Global Themes, look for it and Apply.
This single action sets simultaneously:

* Global Theme
* Application style (Fusion in this case)
* Plasma Style
* Colors
* Window Decorations
* Icons
* Window Management / Task Switcher (Grid)

but I am not able to set

* Application Style, GNOME GTK Application Style

I can just set it manually by clicking on Configure GNOME/GTK Application Style button, then Get New GNOME GTK Application Style, look for it, Install and select it.

Is there a way to include this settings into the Global Theme ?
Thank you very much
Vincenzo