Hi @benedictpayot, 

Thanks for sharing your idea with us! You are correct, you are able to add multiple values to a single Profile Property. The kind of Data Type that can hold multiple entries is called an Array or List Data Type. It was a good idea to potentially update Profile Properties by Using Buttons or Links, however, this option isn’t good for storing Array Data, as it can only hold one value. This is the reason why you’re seeing the data currently being overwritten. A potential workaround would be to send a Campaign to the audience you want to target and call them to update their ‘Manage Preference Page’ to reflect what products they’re interested in. You can update your ‘Manage Preferences’ Page in your account to include a checkbox with all the options of products you want to include, as checkboxes are designed to hold multiple values at once.

I’d recommend checking out these other posts by the Community on updating their ‘Manage Preferences’ Pages to accomplish the same thing: 

https://community.klaviyo.com/lists-segments-and-profiles-35/ask-people-to-fill-in-details-about-themselves-581 

https://community.klaviyo.com/lists-segments-and-profiles-35/collecting-customer-interest-in-specific-product-category-545

An additional option would be to create a Klaviyo Form to display only to your intended List/Segment of current subscribers and use a Checkbox option to collect the List Data. 

Thank you for sharing in the Community! 

Best,

Taylor