Domoticz

If you click the Log at a widget, you get the graphic display, and there can opt for export of an actually displayed graph-segment by clicking the desired format in the Chart context menu in upper right corner in that graph.
Sometimes such graphic export is just enough: no Grafana required.

However, that export is oneshot.
Is there a capability to have periodic retrieval of such graphic file?
If not standard included somewhere in Domoticz, has somebody developed a related schript?

I remember it was discussed before on the forum, searched for but could not find it.

I thought the conclusion was that it is not possible to script this yet as there was no command from server side to do this. The graph is created by the browser.
It is possible to export the history values by a http command to CSV. You could use that to create a graph in excel.
https://domoticz.com/forum/viewtopic.php?t=30825 or viewtopic.php?t=30725

Exporting as csv-file to excel and subsequentely generating a graph is exactly not my intention (trying to limit effort to get a simple graph in q quick&lazy way).
But perhaps your statement

The graph is created by the browser.

might be an entry, if it is possible to emulate the call by the browser by means of a script.

Requires some inventive thinking how to make that emulation, cleanly pointed to Chart context menu of a selected graphic window in Domoticz' widgets.