Donald Trump is everywhere these days - putting together a pro football team with multimillion-dollar contracts, hinting at stepping into the huge Lincoln West housing development, telling the Governor and Mayor where they ought to build the projected sports complex, talking about erecting the world's tallest building. And, oh yes, he also spent some time trying to obstruct a group of his tenants from putting up a Christmas tree in their lobby.

It's very hard to understand why young Donald - busy as he is making cosmic decisions - would bother himself with a matter this petty. But the mogul-statesman has become so upset at the tenants of 100 Central Park South - because they're not too keen about his desire to throw them out, tear down the building and put up a bigger and glossier structure - that he has lapsed into tantrum and been behaving like a slumlord.

Ever since he bought the nice 15- story apartment house (across from the St. Moritz Hotel, views of Central Park) two and a half years ago, he has been bedeviling the tenants, with a view to eviction.

He brought specious lawsuits against some of them, and judges have thrown these out, charging him with ''bad faith,'' ''harassment'' and ''intimidation'' - in one case ordering young Donald to pay the tenant's legal fees. Also, he proposed putting some of the city's homeless people into the dozen or so apartments he has already emptied in the building. The city smelled a scheme to use the derelicts to scare out the rest of the tenants, so it correctly declined the offer. Then Young Donald's bluff was called. A well-known refugee organization, the International Rescue Committee, asked him, since the homeless idea had been rejected, if he would instead take in Polish exiles from the Solidarity movement on a temporary basis. His office said no - the offer was only for ''people who live in America now, not refugees.'' Meanwhile, Donald was not treating his tenants who live in America very well. He hired a new company with a tough reputation, Citadel Management, to run the 100 Central Park South building. Services began to decline, repairs weren't made. The luxury building turned shabby. He has tinned up the windows of vacant apartments that face Central Park, giving the facade a grotesque look. Young Donald says this is for security, but the back windows of the same apartments, easier to break into, are not tinned up. Moreover, under Citadel Management, the building's security has been porous, with several burglaries - very rare before Trump ownership - in the last couple of years.