You can edit the Collapsible Row in Online Store > Theme > Customize.
If the content of the collapsible row is the same for all product pages, simply click on Add block > Collapsible row and insert the content in Row content.
Otherwise, in order to add different content for each product, you first need to create metafield and then connect it with your theme setting to display metafield on your online store:
Create Metafield by going to Setting > Metafields > Products >Add definition > fill out the required info.
Go to Products > Within each product page, scroll down to the bottom and you’ll see the metafield you’ve created before, then fill out the specific content for each.
Navigate to Online Store > Theme > Customize
Select Products then Default Product from the page selector at the top
Within the sidebar menu, click on the click on Add block > Collapsible row > click on the Insert Dynamic Source as the photo attached below > Select the associated metafiled
This suggestion of yours is also very helpful, I have some content that really needs to do this.
But I have different “description” content for each product, and there is a lot of text, so I have to find a way to fold them, I don’t know much about code, so maybe I can try it with a plugin
Regarding your question about adding different subtitles to each product, you’ll need to create a metafiled for product subtitles and then go to theme customize to add a text blocked linked to the product subtitle.
I’m replying here because my objective is along these same lines. I’ve followed the above instructions, but get stuck at adding my metafield to the Collapsible Row.
It gives me the option to insert Nutrition, my Multi-line text metafield but doesn’t show my other existing metafield, Nutrition-Info, which is a file (it displays an image of the nutrition label.)
Any suggestions on how to insert the image Metafield?