There are 3 locations where you can rename tags:
On the dashboard
To rename a tag, open the dashboard settings on the left panel. Click on the edit icon near the target tag, make edits, and save the changes.
On the Tag page
Open the Tag page and click on the pencil icon near its name. Edit the name and press Enter or click somewhere on the dashboard to save the changes.
In the Tags section
Go to Workspace > Taxonomy > Tags. In the 'Actions' column, select the 'Edit tag' action.
On the new page, change the tag name and save the changes.