You can check by two methods, both shown in this quick video:
https://www.loom.com/share/0955a870d5c9497a837268058613824a
Method 1: Under WooCommerce, Click Add-on Groups. Click Groups tab. An Add-on will show which products it’s assign to show. You can view by reviewing the column labeled “Products” or click on the add-on.
Note: If All is showing, this means it applies to all products.
Method 2: Click on a specific Product. Under the product data section, you will see a tab labeled “Product Add-ons”, click on the tab. If the product is assigned to an Add-on group, this group name will show. If the product is not assigned to an Add-on group, no group name will show. For example, in the video. Product Sunglasses is assigned to the Add-on named Sunglasses. Product Cap is not assigned to any Add-ons.
I hope this helps.