For having different tab content for each product, you need to use product metafields:

  1. From the Shopify admin, go to the Product's Metafields settings (Settings > Custom data > Metafields  > Products)

  2. Click on "Add definition"

  3. And add something like this:

    Screen Shot 2021-12-09 at 11.57.06.png

  4. Save it and go to the product you want to set it's dimensions information (Admin > Products > Product).

  5. There you will find a new "Metafield" input field named "Product dimensions":

    Screen Shot 2021-12-09 at 12.00.08.png

  6. Fill the content for that product and save the changes.

  7. Go back to the "Collapsible tab" block on the Theme editor (Online Store > Customize > Product section > Collapsible tab block) and on the "Tab content" input field click on the dynamic source icon:

    Screen Shot 2021-12-09 at 12.08.15.png

  8. Once clicked, it will show you all the "dynamic sources" available, select the one you just created. In our case, it was the "Product dimensions" option:

    Screen Shot 2021-12-09 at 12.10.45.png

<aside> ⚠️ Find more information about the new Metafields functionality in: https://help.shopify.com/en/manual/metafields

</aside>