Hi there,
Glad you’re enjoying it!
Unfortunately, that’s not possible without javascript (which would be hacky and jumpy), as the elements aren’t direct siblings.
What you could try is adding the content you wish to show in a hook above the sidebars using a hook.
1. Add a Hook Element: https://docs.generatepress.com/article/hooks-element-overview/
2. Set the hook to generate_after_primary_content_area
3. Add your content like this:
<div class="hide-on-desktop hide-on-tablet">
Your content you wish to show on mobile, above the sidebar here.
</div>