State Flexibility for Family First Transitions Act This bill provides states with the option to extend by two years a child-welfare demonstration project scheduled to end in FY2019. A state extending a demonstration project shall provide a plan to the Department of Health and Human Services specifying how the project will transition by FY2021 to comply with provisions in the Bipartisan Budget Act of 2018 relating to childcare institutions, foster family homes, and assessment standards for qualified residential-treatment programs.