how to make this show alert for yesterday or past tasks that has not completed yet?

[Moanrisy]

It only work for current date (today).

(use-package org-alert
  :ensure t
  :config
  (setq alert-default-style 'libnotify)
  (setq org-alert-interval 300
      org-alert-notify-cutoff 10
      org-alert-time-match-string "\\(?:SCHEDULED\\|DEADLINE\\):.*\\(?:\\[\\|<\\).*\\([0-9]\\{2\\}:[0-9]\\{2\\}\\).*\\(?:\\]\\|>\\)"
      ;; org-alert-notify-after-event-cutoff 600)
      org-alert-notify-after-event-cutoff 3000)
  (org-alert-enable))

I already set after-event-cutoff into 3000 min too, which means yesterday task should be shown on alert too (1 day is 1440 min)

[ntBre]

Thanks for the report! I think you will also need to modify org-alert-match-string, which has a default value of "SCHEDULED>=\"<today>\"+SCHEDULED<\"<tomorrow>\"|DEADLINE>=\"<today>\"+DEADLINE<\"<tomorrow>\"". This is where the today and tomorrow values are set for the initial search for agenda entries. It sounds like you'll want to add something like <yesterday> here, assuming Org mode supports that. We pass org-alert-match-string to org-map-entries, so the documentation for that function might help you to craft your match string.

I vaguely remember messing with this in the past and having some trouble, but hopefully it will work for you.