Best approach for a Custom Styled Confluence Header

I’m coming from the Confluence server product, where I created a few ‘user macros’ to create preset ‘panel macros’ to act as obvious headers for our documentation. We’ve been using this for years, and it unifies our documentation, makes changes in context very obvious, and reduces questions.

We simply want a stylized div that we can type a simple string into. I’m trying to use forge so that we don’t have to deal with hosting the resources. However, UI kit doesn’t expose div tags, and custom UI’s iFrames are at minimum, 4 times the height of the header bar, not to mention the nasty scrollbar.

Any suggestions or solutions?

Tried using UI kit and SVG, but scaling is an issue due to lack of control over the styling of the image tag:

The last outcome is the desirable one, with the SVG properly filling the width while maintaining a locked height, but it’s only behaving because I edited the HTML via Browser Dev Tools.

Between the custom UI’s oversized viewport, and UI Kit’s lockout of styling, I’m not seeing a path forward. Any suggestions?