Left-clicking a window's button in the Task Manager widget will bring the window to the front and focused. But if the window is already front and focused, it will minimize the window instead. If there a way to disable this minimizing behavior?

Seriously? NO answer whatsoever after over half a year???

Honestly, I'm not joking here: The ONLY time I've ever gotten any actual help for KDE was when I completely disregarded this forum entirely and posted my help request as an issue on the bug tracker. Almost every single thing I've ever come to this forum for has resulted in NOTHING. What good is this forum then, and why shouldn't users just simply take everything straight to the issue tracker where they won't be ignored?

I can't speak for everyone, but in my case I did see this when you posted it but passed it by hoping one of the other regulars would come by and answer it. However, there aren't that many regulars and it looks like the other regulars either missed it or passed by it without answering (an unfortunate reality of these forums is that the amount of assistance being requested outweighs the amount of assistance being provided (with some exceptions as I know some specific subforums do have more regulars and get quick responses)).

My first inclination for this is to check the settings for the task manager widget you're using to see if you can find such an option. You can also try out some of the alternative task manager widgets to see if any of them behave or have options to be configured to behave the way you expect.
If there is not such an option then I'd suggest you go ahead and file a request to bugs.kde.org.