Hi there –
Thank you for your feedback. This is a feature you can vote on here: https://support.wix.com/en/article/editor-x-request-adding-a-pre-loader-to-your-site-without-code
And when it will be available, we will announce it here on the Forum.
Have you tried creating a preloader like this using multi-state boxes? This uses Velo on both Wix and Editor X: https://www.youtube.com/watch?v=qgPatm-wvRU
Aaron