override-keymap.el

(defun insert-hello ()
  (interactive)
  (insert "hello"))

;; Define a function to cancel the keymap override
(defun cancel-override ()
  (interactive)
  ;; Remove the override from `minor-mode-overriding-map-alist`
  (setq minor-mode-overriding-map-alist
        (assq-delete-all 'copilot-mode minor-mode-overriding-map-alist)))

;; Create and populate the new keymap
(defvar my-override-keymap (let ((map (make-sparse-keymap)))
                              (define-key map (kbd "h") 'insert-hello)
                              (define-key map (kbd "j") 'cancel-override)
                              map)
  "Keymap for temporarily overriding `copilot-mode'.")

;; Function to activate the keymap override
(defun activate-my-override ()
  (interactive)
  (make-local-variable 'minor-mode-overriding-map-alist)
  (let ((override-entry (assq #'copilot-mode minor-mode-overriding-map-alist))
        (composed-keymap (make-composed-keymap my-override-keymap copilot-mode-map)))
    (if override-entry
        (setcdr override-entry composed-keymap)
      (push (cons #'copilot-mode composed-keymap)
            minor-mode-overriding-map-alist))))