There are a couple of plugins that support globally scoped style tags.

https://www.npmjs.com/package/svelte-preprocess-css-global

https://www.npmjs.com/package/@ctx-core/sass

This naturally leads to the pattern to have both a global & a non-global style block for a component.

<style type=text/scss global>
</style>
<style type=text/scss>
</style>
<style type=text/css>
</style>

Unfortunately, Svelte gives an error You can only have one top-level <style> tag per component. Since there is some usage of global style tags, along with a rfc, it's time to modify this requirement if there are <style> tags with different attributes.