プログラマブルでないグループウェアだってスケジュールをSlackへ通知できるんですよ - Qiita

{ "manifest_version": 2, "name": "NotifyYourGwSchedule", "version": "1.0", "description": "Notify your schedule", "icons": {}, "content_scripts": [ { "matches": ["{Your GW's URL}"], "js": ["main.js"], "run_at": "document_idle" } ] } 'use strict'; const WEBHOOK_URL = '{Set your webhook url}'; const BUFFER_TO_START_MIN = 5; const postToSlack = (json, msgKey) => { const request = new XMLHttpRequest()