Currently, it’s not possible to export chart images in a workflow. I’ve seen a customer who used the HTML mode and lots of expressions to produce a dashboard with (SVG?) gauges and charts in it, but that’s a lot of very tedious work. Very impressive, though.
Perhaps, it can be done using an Excel spreadsheet as a template, populate it with data in EasyMorph and then run some VBA macro to save a chart from the template as a file. This article can be a starting point: Running VBA Macros from the Excel Command action