You are partially right. SCOTUS has no jurisdiction today, nor will it have certiorari jurisdiction until there is a final judgment of the NY Court of Appeals.
However, if and when Trump is put in jail or placed under some other judicial restraint (“state custody”), then he could file a petition for writ of havens corpus directly with SCOTUS under 28 USC s. 2254. SCOTUS rarely grants such petitions that are not filed in district court first, but it does have jurisdiction.
Of course, the NY judge could avoid this by simply allowing Trump to remain at liberty pending his appeal.
*habeas corpus, not “havens corpus” of course