Generated chart filename

Hi
I am using an event to create a chart but don't know what the filename is. From the device history chart page I can get to a chart which is called something like this:

_6d8d846b-101c-44ec-98a5-b95199767b64_full.png

but these names seem to change. Can I set the name so it's always the same when generated from an event? (for use in HSTouch)

Also, where can I get the documentation for this excellent plug-in?

Thanks
Robert