The best way to uninstall the app from a store would be perform this from the app itself.
To do this, go to Plan tab in the app page and click "Remove all Smarketly code from store".
After confirming, clicking this button will remove all the app code from your store and uninstall the app itself.
You do not need to do anything else after completing this step, the app will have all the code safely removed.
If you've uninstalled the app via Shopify directly, there will be some code unavoidably left behind.
Unfortunately Shopify has no means to automatically remove integrated code upon uninstallation of an app via Shopify, because as soon as the app is uninstalled they revoke access to the store - so nothing can be done by the app anymore.
The Shopify team has indicated that they are working on improving this process. You can check out Shopify discussion forums for more on this topic.
The code left behind is harmless, however it can be removed by choosing one of the following options to keep things clean:
1. Automatic - You can install the app back onto your store temporarily, go to plan section and click "Remove all Smarketly code from store"
2. Manual - You can manually remove all the code the app generates on your store by following our short guide on how to do this manually. (Attached file "How to remove Smarketly App Builder Editor code from Shopify store.pdf").
After that completing of the options above you should be good to go.
Ask us for help!
If you need help getting things uninstalled please contact our support team.