If you are using Shopify 2.0 OS theme, you can create separate product templates for each type of product so you can add a size guide block for product type A and not for product type B. You can learn more about creating a new template by following this instruction
Hello @jsngn
you can create a different template for different product
For e.g create a separate template for mobile cases and separate for belts with this way you can disable the size chart on mobiles and enable on belts.
How to create a template.
Go to Online store--------------> Themes ----------------->Customize----------> follow these steps bellow:-
I understand you are looking to provide a Size Chart for specific products.
If you are not able to make desired changes using code, then you can take a look at the Shopify Apps that provides features to implement Size Chart for specific products.
But I think the point here is the setting for size chart is fixed for the theme setting. That’s mean I only can turn on or turn off for the whole theme, can’t turn on or off for separate template