Importantly

наречие 1) важно, значительно, существенно Например: more importantly — что ещё более важно, более того Синоним(ы): weightily, momentously 2) с важным видом, важничая

Большой англо-русский словарь

Importantly

adverb 1. in an important way Example: contributed importantly to the language of the field — Ernst Mayr Example: cleared his throat importantly and waited — E. K. Gann Example: the real story is importantly different — Alexander Woollcott 2. it is important that Example: more importantly he stands a chance of having his publication barred — H. L. Mencken Usage: A number of commentators have objected to importantly as a sentence modifier (sense 2) and have recommended important instead. Actually both the adverb and the adjective are in reputable standard use in this function. Important is always used with more or most Example: had bronze weapons and composite bows; more important, they utilized the horse and war chariot — Harry A. Gailey, Jr. Example: second and most important, the book contains no important woman character — F. Scott Fitzgerald. Importantly is somewhat more flexible in not requiring more or most Example: sticks and, just as importantly, unsticks easily — Phoebe Hawkins Example: importantly, the leaven in the mixture is quality — George O'Brien.

Merriam-Webster's Collegiate Dictionary