Usability: configure Kmail message list

Here is another example of a great software, that works great, but which in many ways is not completely usable for the average user (me!).
I have been using kmail for 10 years, and I am very happy about it. I know it well. However, for some reasons I lost some settings (appearances), and I was fumbling around to restore the layout that I liked and that I was used to.

Everything is configurable, and that's one of the things I like a lot about KDE in general. However, the problem is that it often far from clear which setting correspond to what. And this bug report is one example of a long-term user who was completely lost in the settings.

After a few days, I finally found what I was looking for. In configure kmail > appearance > Message list > Default aggregation: the value had changed (I forgot the exact circumstances that lead to the change) to "Activity by date, threaded" and what I used to have was: "Current activity, threaded". Compare both within a folder with lots of emails dating back months if not years up to now, and you'll see the difference.

The problem is that it took me days to figure out that this what I was looking for. It was double-plus unclear to me what the difference was between the two. Also, I looked in many different places, include the "Date Display" setting right underneath, which (of course) didn't seem to restore what I wanted.

So, how could kmail's settings be made more user friendly, more usable?
Here are some ideas:
- provide a screenshot with arrows pointing out what parts would be affected by which setting.
- provide a preview panel which is updated in real time as the user changes the settings, so that it's immediately clear what is affected and how it is affected.
- ???

But again, I love kmail and KDE. I just wish it could simply become the best to the point of being pointed out for its usability and user-friendliness.