A custom identifier without the time separator

The default Denote identifier consists of the date as ‘YYYYMMDD’, then the letter ‘T’, and then the time as ‘HHMMSS’. Users who do not want the letter ‘T’ there can use the following:

(setq denote-get-identifier-function #'my-denote-generate-identifier-without-time-separator)

(defconst my-denote-date-identifier-format-without-time-separator
  (replace-regexp-in-string "T" "" denote-date-identifier-format))

(defun my-denote-generate-identifier-without-time-separator (initial-identifier date)
  "Generate an identifier based on DATE.

If INITIAL-IDENTIFIER is not already used, return it.  Else, if it is
possible to derive an identifier from it, return this identifier.

Else, use the DATE.  If it is nil, use `current-time'.

Slightly modified version of `denote-generate-identifier-as-date'."
  (let ((denote-used-identifiers (or denote-used-identifiers (denote--get-all-used-ids))))
    (cond ((and initial-identifier
                (not (gethash initial-identifier denote-used-identifiers)))
           initial-identifier)
          ((and initial-identifier
                (string-match-p denote-date-identifier-regexp initial-identifier)
                (date-to-time initial-identifier))
           (denote--find-first-unused-id-as-date initial-identifier))
          (t
           (denote--find-first-unused-id-as-date
            (format-time-string my-denote-date-identifier-format-without-time-separator (or date (current-time))))))))