Do they still have that form?  Looks like now it's

502LU Legislative Updates Addition/Subtraction Modifications *(New Form)*

And it looks like it was just issued on April 15.

ANNAPOLIS — Comptroller Peter Franchot announced Thursday, April 15, that all individual Tax Year 2020 tax forms have been updated and are ready for use by taxpayers and tax preparers, effective immediately.

Franchot has extended the Maryland deadline by three months to Thursday, July 15, in order to help families and small businesses experiencing economic hardship due to the pandemic. The extension applies to individual, pass-through entity, fiduciary and corporate income tax returns, including first and second quarter estimated payments.

https://www.heraldmailmedia.com/news/state/revised-maryland-individual-tax-forms-are-ready/article_d...