It’s almost 2024, rapidly approaching 4 years. This is not a complicated request. I’m sure it would take no more than 5 to 10 minutes to code the ability to the store owner’s hands. The fact that 5.6 million Shopify stores send the EXACT SAME subject line to literally tens-of-millions customers is probably the reason Gmail sends ~50% of Shopify emails directly to SPAM.
Get on it.