Hello,
For this task we recommend you to use mergeDocxAt , which allows getting a DOCX content with the relationships (charts have internal relationships) and add it after a specific position of the document.
On the previous API page and the package you can find a sample of using it. DOCXPath folder includes many other samples to illustrate using the referenceNode option.
If the DOCX contains more content than the chart to be imported, you can use removeWordContent to clean it before importing it.
Regards.