While Klaviyo's built-in button options don't allow for campaigns, you can custom code a button that include a campaign using HTML.

The following code block shows an example of using HTML to custom code a button for cancelled subscribers to click and reactivate their subscription at a discounted price 

<p>Come back to us and get a discount code cause you deserve it.<br />
{% with activeSubs=person.rc_all_subscriptions|dictfilter:"status == CANCELLED" %}
{% with prepaidSubs=activeSubs|dictfilter:"is_prepaid == 0" %}
{% for sub in prepaidSubs|slice:"0:2" %} 
<a href="https://wilsons-testing-store-sci.myshopify.com/tools/recurring/quick_actions/{{ person.rc_customer_hash }}/process?action=reactivate&action=apply_discount&subscription_id={{ sub.subscription_id }}&discount_code=<DISCOUNTCODE>"> <button> Click here to reactivate</button></a>
your subscription for {{ sub.product_title }}
<br />
{% endfor %}
{% endwith %}
{% endwith %}
</p>

Adjust the campaign link and language to best fit your needs, and customize the appearance of the button with CSS to seamlessly integrate with your notification's branding.