The phrase "a string of important" is correct and usable in written English.
It can be used when referring to a series or sequence of significant items, events, or concepts.
Example: "The report highlighted a string of important findings that could impact future research."
Alternatives: "a series of significant" or "a sequence of key".
In the 60's a string of important articles and essays were published.
After his pioneering work on ribonuclease, he led a team that produced a string of important new pharmaceuticals.
Now, Platte International (UK Ltd hasshutut down, leaving behind it a string of important but unanswered questions.
The scheduled air service was the latest in a string of important changes between the nations since President Obama decided in 2014 to restore diplomatic relations with Cuba.
The creation of the Federal Office for the Prosecution of Nazi Crimes in 1958 marked a breakthrough, resulting in a string of important prosecutions and trials.
Palmer is tasked with investigating the disappearance of Dr. Radcliffe (Aubrey Richards), who is the latest in a string of important scientists to vanish.
In July, for example, Mrs. Clinton reassured Vietnam and the Philippines by announcing that the United States would be willing to help resolve disputes between China and its neighbors over a string of strategically important islands in the South China Sea.
He delivered a string of culturally important films there, including satirical examinations of war, like "The Americanization of Emily" (1964) and "Catch-22," which identified him as part of a seismic shift in Hollywood's balance of power toward a new generation of young filmmakers.
Normandy was controlled via various interlocking networks of ducal, ecclesiastical and family contacts, backed by a growing string of important ducal castles along the borders.
FEW people know it, but James T. Lee, the grandfather of the late Jacqueline Kennedy Onassis, was a prolific developer who built an unusual string of important New York City buildings, including 740 Park Avenue, which became her childhood home.
How could a maverick with virtually no formal education pull off such an uncanny string of important inventions?
