Code change:
This adds several new specialty identifiers for requests and responses to cover the method, authority, scheme, origin, path, query, and status code values of the HTTP message. It also edits the identifier's associated value to remove the verb and the string construction rules and instead align with HTTP Semantics.
NAME I haven't added references in yet but I tried to move the language in the direction you are suggesting. NAME I added the target-uri field we discussed, please review the text.
Responded to comments and updated normalization rules, please re-review.
Folding in this PR to the main document, discussion can continue on specifics of identifiers and their values as needed.

Related discussion:
text: Note that an HTTP message could contain multiple signatures, but only the signature parameters used for the current signature are included <del> in this field. </del> <ins> in this entry. 2.3.2. The "@method" identifier refers to the HTTP method of a request message.  The value of is canonicalized by taking the value of the method as a string.  Note that the method name is case-sensitive as per SEMANTICS Section 9.1, and conventionally standardized method names are uppercase US-ASCII.  If used, the "@method" identifier MUST occur only once in the signature input. For example, the following request message: Would result in the following "@method" value: If used in a response message, the "@method" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.3. The "@target-uri" identifier refers to the target URI of a request message.  The value is the full absolute target URI of the request, potentially assembled from all available parts including the authority and request target as described in SEMANTICS Section 7.1. If used, the "@target-uri" identifier MUST occur only once in the signature input. For example, the following message sent over HTTPS: Would result in the following "@target-uri" value: If used in a response message, the "@target-uri" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.4. The "@authority" identifier refers to the authority component of the target URI of the HTTP request message, as defined in SEMANTICS Section 7.2.  In HTTP 1.1, this is usually conveyed using the "Host" header, while in HTTP 2 and HTTP 3 it is conveyed using the ":authority" pseudo-header.  The value is the fully-qualified authority component of the request, comprised of the host and, optionally, port of the request target, as a string.  The Authority value MUST be normalized according to the rules in SEMANTICS Section 4.2.3.  Namely, the host name is normalized to lowercase and the default port is omitted.  If used, the "@authority" identifier MUST occur only once in the signature input. For example, the following request message: Would result in the following "@authority" value: If used in a response message, the "@authority" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.5. The "@scheme" identifier refers to the scheme of the target URL of the HTTP request message.  The value is the scheme as a string as defined in SEMANTICS Section 4.2.  While the scheme itself is case- insensitive, it MUST be normalized to lowercase for inclusion in the signature input string. For example, the following request message requested over plain HTTP: Would result in the following "@scheme" value: If used in a response message, the "@scheme" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.6. The "@request-target" identifier refers to the full request target of the HTTP request message, as defined in SEMANTICS Section 7.1.  The value of the request target can take different forms, depending on the type of request.  For HTTP 1.1, the value is equivalent to the request target portion of the request line.  If used, the "@request- target" identifier MUST occur only once in the signature input. The origin form value is combination of the absolute path and query components of the request URL.  For example, the following request message: Would result in the following "@request-target" value: The following request to an HTTP proxy with the absolute-form value, containing the fully qualified target URI: Would result in the following "@request-target" value: The following CONNECT request with an authority-form value, containing the host and port of the target: Would result in the following "@request-target" value: The following OPTIONS request message with the asterisk-form value, containing a single asterisk "*" character: Would result in the following "@request-target" value: If used in a response message, the "@request-target" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.7. The "@path" identifier refers to the target path of the HTTP request message.  The value is the absolute path of the request target defined by RFC3986, with no query component and no trailing "?" character.  The value is normalized according to the rules in SEMANTICS Section 4.2.3.  Namely, an empty path string is normalized as a single slash "/" character, and path components are represented by their values after decoding any percent-encoded octets.  If used, the "@path" identifier MUST occur only once in the signature input. For example, the following request message: Would result in the following "@path" value: 2.3.8. The "@query" identifier refers to the query component of the HTTP request message.  The value is the entire normalized query string defined by RFC3986, including the leading "?" character.  The value is normalized according to the rules in SEMANTICS Section 4.2.3. Namely, percent-encoded octets are decoded.  If used, the "@query" identifier MUST occur only once in the signature input. For example, the following request message: Would result in the following "@query" value: The following request message: Would result in the following "@query" value: 2.3.9. If a request target URI uses HTML form parameters in the query string as defined in HTMLURL Section 5, the "@query-params" identifier allows addressing of individual query parameters.  The query parameters MUST be parsed according to HTMLURL Section 5.1, resulting in a list of ("nameString", "valueString") tuples.  The REQUIRED "name" parameter of each input identifier contains the "nameString" of a single query parameter.  Several named query parameters MAY be included in a single signature input.  Single named parameters MAY occur in any order in the signature input string. The value of a single named parameter is the the "valueString" of the named query parameter defined by HTMLURL Section 5.1, which is the value after percent-encoded octets are decoded.  Note that this value does not include any leading "?" characters, equals sign "=", or separating "&" characters.  Named query parameters with an empty "valueString" are included with an empty string as the covered content value. If a parameter name occurs multiple times in a request, all values of that name MUST be included in separate signature input lines in the order in which the parameters occur in the target URI. For example for the following request: Indicating the "baz", "qux" and "param" named query parameters in would result in the following "@query-param" value: If used in a response message, the "@query-params" identifier refers to the associated value of the request that triggered the response message being signed. 2.3.10. The "@status" identifier refers to the three-digit numeric HTTP status code of a response message as defined in SEMANTICS Section 15. The value is the serialized three-digit integer of the HTTP response code, with no descriptive text.  If used, the "@status" identifier MUST occur only once in the signature input. For example, the following response message: Would result in the following "@status" value: The "@status" identifier MUST NOT be used in a request message. </ins> 2.4.