Other people cannot read minds provide detail.
Screenshots for these types of things are next to useless that could be any of the dozen personalization apps on the app store, or an integrated theme customization.
Merchants that want to buy an MVP for product personalization with theme customization can contact me at firstname.lastname@example.org with store url, use case details and budget.
Thanks for reaching out about this.
There are a few product customization apps on our Shopify App store, so it's hard to confirm which particular app this could be. It may also be that the particular store has customized their theme to include this functionality straight onto their theme's coding, as Paul mentioned.
In saying this, I went through some of the product customization apps on our Shopify App store, and was able to find a few that you can look into, with the first on the list being the most similar visually to the example you gave. Feel free to take a closer look at them:
Please note that these apps are made by third-party developers outside of Shopify. So if you need more information about each respective app’s functionality, I recommend getting in touch with the app developers as they are best equipped to answer app specific queries.
Adding a product customization app such as one of the ones above can improve customer experience overall for your store. If you're selling custom products, it eliminates the step for customers in having to reach out directly to you about personalizing their products. If you're looking to continue bettering customer experience for your store, feel free to have a look at this blog on mastering customer acquisition and retention. It will help you unpack how you can provide exceptional customer experience which will hopefully translate into increased customer loyalty and positive brand imagery.
Let me know how you get on with the information above! I'd be happy to help if you have any other questions.
No worries at all, @lilianamc, happy to help! Don't hesitate to reach back out if you need any further assistance as you continue to work on your store.
All the best!