KStart > Favorites > Configure Desktop > Window Behavior >
renders a number of options for
If you right click the title bar of a KDE window, e.g., Konsole then select
Advanced > Special Window Settings
you end up at the same place.
If from the latter you then change something this automatically creates a Window Rule with which you can set all manner of things.
Similarly, from the former, choosing Window Rules gives you a screen where you see a list of your existing Window rules and options
Unfortunately, you can configure away happily and KDE will just as happily ignore your settings until you middle click the maximize button!!!
Now... that is intuitive... NOT.