For detailed installation and usage instructions, please refer to the blog article below.
https://blog.hapicom.jp/entry/2023/09/12/130526

【Note 1】

If you are signed in with multiple accounts, permission-related issues may prevent the add-on from being installed correctly or may cause the add-on not to work. If a problem occurs, please use the add-on while signed in with only one account.
(How can you create a state where you are signed in with only one account? → Use an incognito window, or use a browser different from the one you usually use.)

【Note 2】

Automatic email sending is configured per account, not per form. Therefore, when multiple accounts jointly edit a single form, please save the sending settings only with the representative account (= the sender email address).

【Note 3: For Google Workspace users】

If you perform “Admin install,” automatic email sending cannot be authorized due to a permission issue. Be sure to perform an “Individual install” and grant permissions to the app through the consent screen.

If you have already performed an admin install, sign in to the Google Admin console (https://admin.google.com/) with an administrator account, remove “Email Notifications” from the domain’s installed apps, and then perform an individual install again.

【Feature description】

◆Response notification email
When the response notification feature is turned on, you will be notified by email each time a response is submitted.

◆Auto-reply email
When the auto-reply feature is turned on, a thank-you email is sent to the respondent.

◆Subjects and messages can be edited freely
You can freely write the subject and message for both the response notification email and the auto-reply email.

◆Variables can be used in the message
Elements that change for each response, such as response results and incremental IDs (numbers that increase sequentially from 1), can be embedded in the message by enclosing them in double curly braces {{ }}. Available variables are shown as a list when you enter double curly braces in the text editing screen.

◆noreply display feature (Google Workspace accounts only)
You can change the sender’s email address to noreply.