NKS5 is a hybrid extension which embeds a Flash-based extension. Flash based extensions are not supported by PS CC 2014 anymore. Please refer to http://blogs.adobe.com/photoshopdotcom/2014/04/photoshop-spring-cleaning.html, http://blogs.adobe.com/jkost/2014/06/installing-the-2014-release-of-creative-cloud.html, and http://blogs.adobe.com/crawlspace/2014/06/2014-release-of-photoshop-cc-faq.html#plugins (scroll down to "Why don’t my 3rd Panels show up in the 2014 release of Photoshop CC? What happened to Oil Paint, Mini-Bridge & Kuler?”)
If NKS5 is necessary for your work, you have to continue to use PS CC (PS CC and PS CC 2014 can coexist) until the author of NKS5 creates a HTML-based version for it.
Thanks for your help.
I'll try my luck with PS CC.
In case anybody else runs into a flash-based issue, Carl Sun is right.
The NKS5 tool palette that wouldn't show up in PhotoShop CC 2014 works just fine in Photoshop CC.