How to add something to a vocabulary?
For instance, we'd like to add the genus Cardiocarpus to the "Genera and species"-vocabulary.
Go to "Content" (right sidebar, scroll down) and click on "Taxonomy". A table with all the used vocabularies is shown. Scroll to the vocabulary which you want to extend. In this case: Genera and species. At the end of the row there are four clickable selections:
Editor; settings; list items and add aitems.