We’re in the process of updating the documentation for Zotero 5.0. Some documentation may be outdated in the meantime. Thanks for your understanding.
How do I merge tags?
Equivalent tags (e.g. “webpage” and “website”) can be merged by renaming one tag to the name of the other. Right-click one of the tags in the tag selector (bottom left of the Zotero pane), select “Rename Tag…” and enter the name of the matching tag.