An abbreviator for which-key descriptions

my-wk-abbrev.el

(defun my/wk-abbrev (prefixstr &optional prefixabbrev)
  "Remove PREFIXSTR from which-key descriptions.
Or, with PREFIXABBREV, replace it."
  (let ((wkabbfuncsym (intern
                       (concat "my/wk-" prefixstr "-abbreviator")))
        (rx (concat prefixstr "-")))
    (setq which-key-replacement-alist
          (append
           which-key-replacement-alist
           (list
            (cons (cons nil rx)
                  (fset wkabbfuncsym
                        (lambda (wkcons)
                          (let ((inkey (car wkcons))
                                (indesc (cdr wkcons)))
                            (cons
                             inkey
                             (replace-regexp-in-string
                              rx (if prefixabbrev
                                     (concat "\\1"
                                             prefixabbrev "-")
                                   "\\1")
                              indesc)))))))))))

Updated and simplified for maintainability.

Updated the short description, since it's no longer a macro.

Updated the docstring.

Updated the example usage in first comment with more abbreviations for Gnus. Also modified to remove the implication that Gnus would need to be loaded first.