You are almost correct. In the if statement when you check for multiple conditions like card_product.handle == 'howah-crew-socks' or card_product.handle == 'howah-gel-orthotic-insoles' you need to use logical operators such as or(||), and(&&). In your case what you want to do is to check if the product handle is ‘howah-crew-socks’ or if the product handle is ‘howah-gel-orthotic-insoles’. So the corrected version of your statement is
{% if card_product.handle == 'howah-crew-socks' or card_product.handle == 'howah-gel-orthotic-insoles' %}
Customize
{% endif %}
So you need seperate the cases with ‘or’ and you can’t do this:
card_product.handle == ‘howah-crew-socks’ == ‘howah-gel-orthotic-insoles’