Sure, here is @Storm 's Shade of Z theme with window transparency:
Here is an example of one of mine also showing transparency:
https://www.deviantart.com/aravisian/art/Predator-Theme-895987019
You may not want "that theme" but it does illustrate the ability.
I am not aware of an educational video that can cover this topic neatly and swiftly. It comes down to learning .css and that is done by practice, practice, practice.
You can start out by creating a gtk.css file and placing it in ~/.config/gtk-3.0
Inside that file, put:
.background {
color: #fff;
background-color: rgba( 10, 10, 10, 0.6);
}
window.csd {
background: rgba( 10, 10, 10, 0.5);
window.dconf-editor {
background: rgba( 10, 10, 10, 0.94);
}
.content-view {
color: #fff;
background-color: rgba( 10, 10, 10, 0.4);
}
Reload the desktop to see the changes.
Using that as a starting point, we can slowly make changes to the different classes to perfect it.