Google has recently announced subscription-based promotions in Google Merchant Center, allowing merchants to offer “Subscribe and Save” style discounts directly through Shopping ads. This enables offers like percentage off, fixed discounts, or free trials for subscription products, helping businesses attract repeat customers more easily.
The feature is now live and available to eligible merchants under Marketing > Promotions. You can find it in the Promotion conditions section.

This update was spotted by Hana Kobzová.