Great question — answering as the UphillTech team:
There are two ways to update a shopify theme. Using Shopify App Manually Add an updated version of your theme to your online store in the following steps Create a backup copy of your existing theme. Visit the Shopify Theme Store and log in. Use the top bar search box to search for your theme. On the search results page, click your theme. Click Add latest theme version or Add theme. More info: How to update shopify theme .
Full answer by Muhammad Afzal: https://stackoverflow.stackexchange.com/a/67001669 (CC BY-SA 4.0).
Want it for your business? UphillTech.