Would be nice to be able to plot a user customisable circle radius around a point, say when working near tall obstacles one can set a minimum distance be it 600 metres, 500 feet or any other value set by the user.

And, maybe linked to a warning notification or highlighted border like you do when approaching or crossing controlled airspace boundaries.

Have you considered creating a custom restricted area or similar for it? That's what the included Data Creator app is for.

Hi Tim, where can I find this Data Creator app? Is it avail on iOS?

No, the app is only available in SkyDemon Plan on PC. But once you have created your custom "airspace" you can save that data to the cloud and load it on your iOS devices.