Examples of default theme content includes the success message when a customer subscribes to your newsletter or the message that's displayed when a customer's search returns no results.
The text customers see when their search returns no results is default theme content
To edit your default theme content:
Under Online Store > Themes, click on the three dots next to the theme you want to edit
Select Edit default theme content
Now either use the filter to search for the exact wording you want to edit, or go through each tab individually.
This default theme content is for your live theme. To edit an unpublished theme's content, you may be able to update the theme ID parameter in the URL and hit Enter. For example, in the following URL you would update the theme ID in purple:
https://admin.shopify.com/store/primavera-distinction/apps/translate-and-adapt/localize/online_store_theme_locale_content?shopLocale=fr&id=179295519069
In the toolbar, select which language you wish to translate
Start editing the content using the sections list in the sidebar
