We have a feature in our app to manage dimensions of the shopify products. All the shopify products will be automatically synchronized to our system after installation of the app. Also merchants can resync products at any time.
You can see all products with product name, vendor, product type and dimension with a search option in the product list page. You can also see a link to update dimension or show product variants which will open a popup with all options.
Product export/import :: You can also export all products into a csv and then manually update all dimensions of the products and then finally import that csv which will update all the dimensions of the product of our system.