How can I create my own KDE styles?

When I go to System Settings and see Global Theme, Plasma, Application Style, Icons, etc. along the left, how can I create my own? What software should I use? What else would I need? Do I need to worry about something called a “theme engine”?

I find it basically useless to click on “Get New Themes” or styles. For instance, I click on Get new global themes and the first selection is “Windows11-Twilight Global Theme”. It shows an image of a white window pane divided up on a pale purple background. I don’t really like that on my computer. I click on it hoping it might indicate something else it might accomplish. It has a couple of other images with pale purple windows with no borders. Guess that’s not for me. So I give up and go down to application style. But there is no get new application style button. Moving on down to plasma style, which I have no idea what it changes, I click on get new plasma styles. And there’s that “Windows11-Twilight” again. So I skip it and look at the next one called, “Kanagawa Plasma”. It has a round circle with what might be some clip-art wave. The other two images are of a brown wave over a mountain. What in the world is this trying to tell me? Ugly picture. I don’t want that on my desktop. But wasn’t I trying to change plasma style, whatever that may be? And it changes my desktop wallpaper?

Do you see what I’m trying to say? Trying to choose a theme or style from the button is pointless because the creators spend more time bragging about their desktop wallpaper than indicating what they are changing.

So how many times do I have to repeat this process?

I may be wrong, but seems to me in openSUSE 11, I could set my border thickness, change my title bar colors, and had lots of control over everything. Now, only certain themes which you have to guess at allows you to change certain things.

So how can I create my own? I might learn where things are located, what things change what.

Oh wow! Thank you!
That will keep my busy for awhile.