This is an example of how to render React component for Highcharts tooltip using React portals. See Chart.tsx and Tooltip.tsx files below. Latest Highcharts version is required for the example to work correctly (9.0.0 at the time of writting).
Codesandbox: https://codesandbox.io/s/highcharts-react-tooltip-ut1uy


Ah, of course. Makes perfect sense. Thanks again man!