Pretty sure the answer to your question is "no". There is an Import tool in Custom Office, but you need to export the Customizations from another system to create the file to be used to import into your target system. I use it when I create the UDFs in a test system and then need to port those over to a production system. I think what you're asking is to just create an import file with UDFs, etc., and import that into your Premium system, which is something different.

How can I export a UDF csv? If I have the UDF design in a csv, I can develop it in excel and then import if possible. Just wasnt sure how to export a csv of the structure of a UDF and import that. 

If you manually set up all the UDF's and screens in a test installation, Custom Office has ability to then Export and Import the Customizations.  It is not a .csv file, but a Custom Office file format for this purpose. UDF's need to be added using the Custom Office Utilities, they can not be imported.  You also have to add each UDF to the screens for the users or user groups that will need to see these new fields.  ###-### is a user group for all companies, all user ID's. 

There are only "copy" functions, so you always have to do such things manually, directly using the Sage 100 custom office interface, at least once.