Hey @bertoalvaro,
Welcome to the community! That’s a good question, and I’m actually consulting my team on this now, to see if we can provide you with a concrete answer. Since you’re editing a form with custom CSS outside of Klaviyo, I can’t reliably say how that will impact how the form behaves, but my hunch is that it will still count as a form view, even when CSS is set to display:none. That being said, it might be worthwhile to test this. I’d recommend adding a form to a rarely-visited page on your site, and hiding the form with CSS, then viewing the page once. Wait a few minutes, and see if a form view is logged in Klaviyo.
Does this make sense? If you have any other questions about this process, don’t hesitate to let me know!