Hello everyone,
I successfully installed Gentoo with Plasma5 for the first time on first try (yay!) and now I am going to fix stuff and ran into an issue with missing buttons in the kde menu as mentioned in the subject.
I followed all these instructions:
https://wiki.gentoo.org/wiki/KDE
One guess is that it could be OpenRC because I actually selected the systemd profile for kde.
I am done with my debug-fu at this point. :)
In the attachment you will find a lot of information. Customized parts are marked with "# custom".
Thanks!
-Ramon