Saving chart images
If you ever need to save or export a chart's image, there are a few ways you can do it.
The easiest way would be to simply right click the chart and then click Save Image As..., like so:
That will download a .png image of the chart as you're seeing it.
An alternative method is to simply screenshot the chart. This can be preferable in some cases. Here are guides to taking screenshots that may help you:
Finally, while this isn't really a method that will let you save a custom screenshot, it's worth noting that the charts included in Digests are all images, so you can just save the chart image sent you in a digest.