Importing a file in RadRichTextBox from any of the supported formats parses the document to the native document model
of the control with base element RadDocument. This model does not have a concept of charts and there is no mechanism for preserving unsupported data when importing. What the control does is it tries to handle the content as best as possible and show the results. For this reason parsing the charts after the import would not be possible and I cannot suggest a way for achieving the desired result.
Genuine support for charts in RadRichTextBox is in our to-do list, but at this point is not scheduled. I created an item in our Feedback & Ideas Portal where you can upvote the feature and be notified for its progress. You can find the item here
Let me know if you have any additional questions.
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