I usually create json files to export/import configurations. You need to create a message definition and mappings that contain all relevant objects and attributes.
The export should be straight forward. Just export via mapping and pass the template.
The import can be more or less complex. Easiest import is an import where you don’t need to update an existing template. You could just create all objects when importing (except the objects from model reflection, they need to be associated only. But that should work. You just need to define a key. The complete name is always a good key for those objects)
There used to be a module for that: https://appstore.home.mendix.com/link/app/16873/Conclusion-Low-Code-Company/Excel-Exporter-Template-Manager
But that one has not been updated in a while and it seems not compatible for Mx8. But it might give you an idear on how to do it.