xfce4-notes-plugin has not seen a release in 4 years however there was some work done in git repository. I just tested that the code there builds fine against current XFCE with GTK2 disabled. In order to preserve the package I propose to add a new snapshot to portage, or alternatively add -9999 ebuild. Note that there is an experimental GTK3 support in currently present version 1.8.1, but I was not able to compile it. Reproducible: Always
