Doesn't seem to work well on Plasma 5.12, it just switches between windows, showing the current window in the foreground and the other windows transparent in the background.

schnelle is right. It doesn't appear on 'Hot new stuff'. Also, how do I configure it? How I use it? How is launched? I installed it with plasmapkg but it doesn't show up under kwin scripts or desktop effects.

Hi

Well KDE makes it a bit difficult to find and activate I have to admit but from KDE 4.10 on there is a GHNS button which is only a icon of a "favorites star" without text. You can find it under System Settings -> Window Behavior -> Task Switcher under Visualization. There is a drop down list of the various installed Window Switchers and next to it the GHNS star button.
Anyway if you have installed it through plasmapkg it should appear there, too.
The confusion is that these switcher scripts won't appear under effects or kwin scripts but only under Task Switchers. After installing it you will find Windows Wall in the drop down list there.

It doesn't appear in "Get Hot New Stuff". I think you should move the effect to "Kwin Effects".

It doesn't appear in "Get Hot New Stuff". I think you should move the effect to "Kwin Effects".