Adding elements to the left and right side of main-outlet in a theme

The plugin is indefinitely supported, so why not focus on just building the bespoke widgets, then you limit what you have to re-invent?

The whole point is that you can create a widget once, then move it around, and change its order relative to other widgets using only settings.

There’s also a compatible custom html widget that allows you to push out arbitrary html, but creating a native widget is ultimately the way to get full integration at the JavaScript level.