You can delete an already taken screenshot of a heatmap by navigating to a heatmap and scrolling to the bottom of the page. If the heatmap is still active and you have at least write access, then you will be able to delete the screenshot.

The screenshot will be retaken in the near future as soon as a visitor views the page again.

If the heatmap is no longer active, it is not possible to delete the screenshot because the screenshot would not be retaken (unless below command is used).

Alternatively, there is an API method such as:

HeatmapSessionRecording.deleteHeatmapScreenshot

As well as a Console command:

./console heatmapsessionrecording:remove-heatmap-screenshot

The console command can also be used to retake the screenshot of an already finished heatmap. In this case, the heatmap will be temporarily restarted and up to 50 new samples will be taken so a screenshot can be taken. Then the heatmap will end automatically.