OpenStreetMap Tags Editor — Zverik

This is a WebExtension that adds an "Edit Tags" button to all node, way, and relation pages on the osm.org website. The button opens a text area for editing raw tags (in form key=value) with a "Save" button to upload changes.

Note that it is essentially a hack, and uses some undocumented authentication holes. Like, you need to have used iD editor to use this one. It can stop working at any time because of the website changes.