Issue No in Auto-Reply Email Subject

I’m currently using the Support module to track customers issues. I have setup the system to automatically create an issue when a customer sends me an email message.

I’m looking for a way to automatically add the issues number (naming series) in the email subject of the auto-reply.

For example, if a customer sends me an email message with the subject “My phone is not working”, then I want ERPNext to auto-reply with an email with the following subject:

Support Case: [ISS-2021-012] - My phone is not working

I know I could use the document reference as {{reference_name}}, but there is no place for me to add this to the subject of the auto-reply.

Could anyone please help me with this?

Thanks in advance.