how can I customize components?

[sfdsfdsr8u657657]

On your demo, this component looks like this:

And on my panel after installation it looks like this:

How can I customize this and other components?

[arturvolokhin]

You can add menuPopupExtraComponents props to <Admin /> component in App.tsx file.
Example of this logic is here - https://github.com/dev-family/admiral/blob/master/src/App.tsx