CCleaner is considered a generally safe cleaner. Thus, all Advanced selections under the Windows tab are unticked by default, presumably for a reason, which may have to do with system stability.

However, in its 8-step Malware Removal Instructions https://www.techspot.com/vb/topic58138.html, TechSpot advises:

My fist question is: What does one gain by including these Advanced selections apart from a little extra space, and even that until it is soon filled up again?

But my main question is: Why does CCleaner leave out these Advanced selections by default? More specifically, what could be the adverse consequences of ticking (selecting) them?

A full item-by-item reply would be most helpful for dispersing (or justifying) fear of selecting them. The tool itself does give some info on each, but this is not always clear. E.g. for Tray Notifications Cache it says “You need to restart the explorer.exe process.” So, how does one restart the explorer.exe process? Don’t we start it anyway every time we click on its icon?