You can completely rewrite the Abannoed Cart e-mail by going to "Settings" -> "Notification" then scrolling to "Abandoned Cart Email". Alternatively, you can turn this off and use a favorite of ours: Klaviyo: Email Marketing & SMS | Shopify App Store that does this with an easier drag&drop functionality.
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Besides the app @JHKCreate suggested, you can also use OrderlyEmails: Email Templates. I use this app in my store and it works really well. It comes with pre-designed themes that you can use for your notification emails (including the abandoned cart email) and customize to your liking. After selecting your theme and designing the emails, you're simply given a liquid template that you can paste and use in place of the default notification templates in Settings > Notifications. It's really easy and convenient to use.
The app takes you through the entire process of designing your notification emails step-by-step so it will be easier to visualize the design process once you install it. If you're interested, feel free to install the app in your store. Should you have any questions about the app, you can contact their support team using the details under the Support section of the listing.
Customizing your abandoned cart email is an excellent way to make it more effective and to differentiate your store from other stores that use the standard notification templates. Before you design it, make sure to take some tips from this blog post that shares best practices and examples of effective abandoned carts. This particular email can bring sales to your store so think carefully of what you're going to add to it so customers are enticed to complete their purchase.