Elem Klimov, head of the Soviet Film Makers Union, has stepped down for a "creative break" in order to continue working as a director. His first new project, already under way at Mosfilm Studios in Moscow, will probably be about Stalin, according to reports from the Soviet Union published in Daily Variety. An earlier plan to co-produce a film version of Mikhail Bulgakov's madcap novel "The Master and Margherita" with an unnamed American company has apparently been shelved. Klimov's leave of absence could last as long as two years, Variety reported in Tuesday's editions. A colleague of Klimov's, Andrei Smirnov, will fill in for Klimov. Klimov was named to head the union after a stormy membership meeting in May, 1986--a session many analysts feel presaged Soviet leader Mikhail Gorbachev's glasnost policy.