DC state return indicates that an "Add Misc Credits & Contributions Form" is needed and not available to file until 01/30/2020. What does this form do?

You are referring to DC Schedule U, Additional Miscellaneous Credits and Contributions.

This schedule lists certain additional non-refundable and refundable credits you may be able to claim. It also lists several contributions funds to which you may wish to contribute.

Nonrefundable Credits

• Out of State tax credit. 
• Alternative Fuel Vehicle Conversion and Infrastructure Credits.
• DC Government Employee first-time homebuyer credit

Refundable Credits

• DC Non-custodial parent EITC
• Keep Child Care Affordable Tax Credit

Contributions

• DC Statehood Delegation Fund
• Taxpayer Support for Afterschool Programs for At-Risk Students
• Anacostia River Cleanup and Protection Fund