Theme Updates - Keeping Custom Code
Whilst it is possible for you to edit your theme's code, any alterations made would not carry over to a fresh update.
The reason for this is because the Shopify platform allows for 20 "slots" where you can save theme installs and duplicates - these are not connected, so any changes you make to one, will not affect another.
Downloading a theme update will reside in one of these isolated slots - this is the same for all themes, both premium and free:
To transfer over any coding adjustments from other theme versions, you would need to speak with a coding customisation specialist.
We have more information on this available here: