Is it possible to edit the values in SharePoint maintained fields (Created Date, Modified Date, Created By, Modified By) during migration?
Yes, you can assign new values for the SharePoint maintained fields - Created date, Modified date, Created by, Modified by and Content type fields using an external metadata file.
You can choose to retain the metadata values for these columns as in source SharePoint or alter /edit the values in these fields during the migration task.
You have to create a new Column Mapping template and edit the desired SharePoint default columns for which you wish to assign values from a metadata file. Select Metadata File for Source and provide the column name containing metadata values for each SharePoint column. Provide the template which you have created in the migration task wizard.
You can refer Column Mapping section in the online help document of Dockit for more details.