Hi Keith thanks for posting in the Lucid Community! I'm happy to help. Good news - Lucidchart supports an import option for draw.io and XML format. To access this on your Lucid home page choose New > Lucidchart > Import > Draw.io.

You can also import directly into an existing document by choosing File > Import Diagram > Draw.io. Next you can upload your XML file which will be converted to a Lucidchart document that you can continue to edit. 

At this time exporting as an XML file is not supported but I certainly understand that this is important for your workflow. The best way to promote this to our development team is via this feature request form which utilizes valuable feedback like this when prioritizing improvements to Lucidchart. Thanks for your use case details here and apologies for any inconvenience. Please let me know if you have additional questions!