yup. it’s an annoyance.
So, if you’re interested in a workaround… I noticed that some of our themes have a bit that adds space at the bottom, to pad the bottom of the screen a little bit.
This is a super simple version of it.
{% if content_for_header contains "previewBarInjector.init();" %}
<div style="height: 50px;">
</div>
{% endif %}
You want this right before the closing </body> tag, but it can be in a snippet, section, or even in theme.liquid. And, the old preview bar was 50px tall, I haven’t looked at the new one.
p.s. a bonus: to check if you’re in the customizer in the page code, you can use {% if content_for_header contains "Shopify.designMode" %}