PRESIDENT REAGAN has quietly abolished the nominating commissions established by President Carter to help select federal appellate judges. Nothing is replacing them just now, the administration says, because it doesn't need any help in filling the existing judicial vacanies and hasn't figured out yet what selection mechanism it wants to use. The president and the administration, however, had better figure out what they want quickly or they will discover they have surrendered an important presidential power the previous administration fought hard to win.

President Carter created those commissions as part of his effort to wrest control of judicial nominations from members of the Senate. He succeeded as far as appellate judges were concerned; almost all of the more than 50 he appointed were his own choices, not those directed by various senators.

That was the first step toward regaining for the White House its rightful role in the selection of judges. The second involves the selection of district judges. President Carter tried to get control of that, too, but failed because many senators are jealous of their "right" to dole out federal judgeships as patronage in their home states.

It is understandable that the Reagan administration did not like the composition of the Carter nominating commissions. They were loaded with supporters of Mr. Carter and had recommended mostly Democrats. But the mechanism is one with which President Reagan is thoroughly familiar. As governor of California, he used nominating commissions to help him select trial judges. All the indications are that the procedure worked well for him there, providing a supply of qualified and politically acceptable appointees.

If Mr. Reagan wants to use that California system in Washington, he should set up his own commissions and give them their orders. If he wants to try something else, he and Attorney General Smith should set the ground rules soon. Otherwise, the Senate will find a way to wipe out all traces of the Carter initiative and Mr. Reagan will join most other modern-day presidents in yielding to the Senate his power to decide who sits on the federal bench.