Extra column when migrating Sybase databases to single SQL Server database

I'm trying to use Microsoft's SQL Server Migration Assistant for Sybase ('SSMA') to migrate multiple Sybase databases (that have the same schema) to a single SQL Server database. All of the tables in the new SQL Server database will have an extra column project_id, which should have a fixed value depending on which Sybase database data is being migrated from. I've migrated the schema using SSMA, and then created the new columns in SSMS. But I the new columns aren't visible in SSMA, and I can't see any way to achieve what I want to do. How can I migrate data from each of the Sybase databases whilst utilising the extra project_id column?