Is it possible to automatically add feature Definitions depending on the layer name?

I do know that you can create a selection set of all the elements on a level, and use the Properties to assign a feature definition to the entire selection set. I'm not sure how that would be automated.

I'm still learning ORD, so hopefully someone with more experience will have a better solution.

There are a set of tools designed for Migrating Features from Earlier versions of Civil Products to Open Roads. This is the link to the Wiki Page:

https://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/36224/feature-migration-into-openroads-designer-connect-edition

You might want to look in the Files area to make sure you have the latest version. There are special instructions on how to enable import and export of XML files of Features Definitions and Feature Symbologies. These can be used with one of the migration tools that converts between the XML files and Excel. Similarly, there is a tool that can convert between an Element Template XML file and Excel. The element Template file will generate a single worksheet Excel File. The Feature Definition and Feature Symbology tool creates multi-tab Excel Files.