The Tags option is located in the Organize menu and allows you to view your list of tags, sorted alphabetically, and view and edit all the items associated with each tag in each of the lists:

The “edit” option (1) allows you to access the tag editor where you can rename the tag you are editing (1) or delete it (2):

If you rename a tag with the name of another tag that already exists, both tags will be merged into one.

Deleting a tag does not remove the entire word from the items that contain it, but only the # symbol. This is done to preserve the meaning of texts where the tag is part of the phrase (such as “#call Mike”).