One of three sets of East-West arms talks takes a step forward

One step forward in Central European troop reductions, one step sideways in chemical disarmament, and a continuing stalemate in ''confidence-building measures.''

This is the tally of the three ongoing arms-control-related talks as they entered their spring recesses.

In all three the prospects of any East-West rapprochement during this American election year are slim.

The step forward came in the West's new proposal Thursday in the Vienna mutual and balanced force reduction (MBFR) talks. After controversy in recent weeks in the inner circle of the United States, Britain, and West Germany, the West finally relaxed its former insistence on prior agreement on existing troop strength data (as indicated by Western intelligence) before any troop reductions could be agreed on.

The West now says it is willing to exclude from the current data Warsaw Pact service support forces whose work corresponds to work done by civilians in the West. And it no longer requires prior East-West agreement on exact data but would accept an understanding ''within an acceptable range of (Western) limits.''

The shift is designed to show goodwill and introduce movement in the 11 -year-old talks. It would allow Moscow a face-saving retreat from their official numbers for Warsaw Pact forces, which the West deems understated by some 160,000 .

West Germany wanted such a flexible Western response to the Soviet expression last summer of a new willingness to accept (undefined) inspections in connection with any agreed troop reductions. Theidea was to set aside the dispute over data for the time being and proceed with initial limited reductions and the on-site verification of those reductions that the Soviet bloc would accept.

But Britain and the US were more cautious. Thursday's proposal still requires prior agreement on data, even if only range rather than exact figures. After such agreement the proposal envisages initial Soviet-bloc and NATO reductions of 30,000 and 13,000 ''combat and combat support troops,'' respectively. At least 90 percent of the reductions would come (as Moscow desires) from units rather than individual soldiers.

The Western proposal would also require ''improved cooperative observation and inspection measures'' for verification.

The step sideways on disarmament of chemical weapons came Wednesday at the UN disarmament conference in Geneva, where US Vice-President George Bush presented the new American draft treaty banning not only use (as in the 1925 Geneva protocol) but also production and stockpiling of these weapons.

Soviet reaction to both the chemical-weapons and the MBFR proposals has so far been negative. Hopes that President Chernenko might wish better relations with the US have been dashed as it has become clear that the Soviets are not convinced that Mr. Reagan will be reelected and therefore have no incentive to make any deals with him that might aid his reelection.

The Stockholm conference on confidence-building measures and disarmament, now recessed, is also in the doldrums. There the West keeps pressing its proposals for ''confidence-building measures'' while the USSR keeps pressing its proposal for treaties renouncing the use of force and chemical weapons and the first use of nuclear weapons.