Hi @Keren,
The answer to this question would depend on how you want to ultimately use this data. To get data into Klaviyo, you have two main options:
An example use case based on your interest in knowing if a customer has left instructions at checkout could be to work with a developer to create an API call that would sync the custom event “Checkout Comments” and in that event, you could pass over the comments provided at checkout. You could then create a flow that triggers when this event happens and then you could send an email internally to the stakeholders that would be needing to know this information to alert them of the instructions.
I hope this helps!
Julie