SOMETHING GOOD may come after all from a presumptuous request by House District Committee Chairman Charles C. Diggs Jr. to meet with President Carter on city affairs. Fortunately by the time the meeting occurred, other members of pertinent congressional committees were included-even though the White House snubbed the elected mayor and city council. What President Carter seems to want is an agenda of enactable federal proposals to which he could give support. That shouldn't take long to submit.

All that's needed to get going is a ranking of the longstanding legislative proposals sought by the city government. For that, the White House should be listening to the very people it didn't get around to inviting before: Mayor Washington, Council Chairman Sterling Tucker and the other council members, including the lone Republican, Jerry Moore, and the Statehood Party's Julius W. Hobson Sr. Leaders of the elected school board, too, may have some solid recommendations. At the congressional level, Delegate Walter E. Fauntroy-the only elected official from this city who was invited to the White House session-can speak from experience about the prospects of various measures. Other officials from the region also have interests in these matters.

The immediate list ought to focus on the city's financial problems: There is the city's huge pension liability, for example, which is the result of an unfunded pension plan established long ago by Congress. It needs urgent federal assistance and restructuring. New congressional authority for an increase in the annual federal payment also is needed. Metro needs federal help. RFK Stadium has money problems. The Metro regional transportation system deserves strong presidential support for federal financing.

Beyond these immediate concerns there is the important matter of full voting representation for the city in Congress. Mr. Fauntroy has worked long and sensitively on behalf of this change and President Carter's active support might well spell the difference between another close-but-short vote in Congress and passage. There are ways the city charter should be changed, too, to give the city more authority to control its budget and exercise other local powers-including changes in the criminal code, an authority that Mr. Diggs prefer to withhold.

So Congress shouldn't be left in a holding pattern waiting for White House clearance to proceed on District affairs. The President wants a task force to prepare the agenda for him. Any such task force ought to do its work with a minimum of meetings and a set of strict dealines so the president's commitment to local self-government can be put to test right here in his new backyard.