Sadly, anything from http://uwosh.edu/ploneprojects is likely to be outdated and no longer applicable to Plone 5. Almost all the sites I and others wrote "how to"s for on that site were Plone 3 and 4. @bledwell and I have tried to get that !@$# site to display publication date but can't get it to work. Otherwise you'd see that that article was written on Apr 16, 2009
thank you for your answers.
I found out, that there is a problem using browser Firefox (52.0.2):
If there is a missing resource required by the bundle, clicking the 'compile' button within 'resourceregistry-controlpanel' will finish in a view, which is indicating the compiling is finished successfully. But there is no generation of the bundle file within portal_resources (of course).
Using browser e.g. Chrome results in a view indicating there is a problem during compilation in the case of missing resources.