Migrator for Notes to SharePoint QuickPlace/Quickr mode stores Source Data Definitions as simple XML files (with a default extension of .QPSRC). You can edit these files using XML editors and even plain text editors. In addition, you can easily distribute them to other users.
By default, Data Definitions live in the DataDefinitions sub directory of your Migrator for Notes to SharePoint program directory, but you can change this location if you want to. See for more details.