I'm eager to learn how to script and hence starting by installing some scripts and seeing how they work. But alas I can't even get that far.

I installed a pile of scripts:

https://flic.kr/p/Com2DR

and yet hardly nay of them show on the Configure Scripts list:

https://flic.kr/p/BZsLv2

and almost none of them appear on the Tools menu as expected:

https://flic.kr/p/CUxsjs

In particular if I take the one example of Selecta:

https://opendesktop.org/content/show.php?content=138497

It's an Amarok 2.0 script it says, and I'm using:

Amarok
Version 2.8.0
Using KDE 4.14.2

If there's a version incompatibility how can I diagnose, I expect some feedback. Is there a log file? I can't seem to find one?

What am I not understanding here?

I fear I can't help much here, as I am not a developer, but if you intend to write scripts, you better work with Amarok 2.8.90, as there have been quite some changes in the scripting stack since Amarok 2.8.0.
We also have a wiki page for the scripting, you can find here: https://community.kde.org/Amarok/Development#Scripting

FWIW: I moved this to the development forum, as it is not strictly speaking a user issue

FWIW2: since we only maintain the scripts we ship, all questions related to a 3rd-party script are better addressed to the script author.