The main thing that trolls seem to be known for in Harry Potter, besides their love of killing/hitting things, is their stupidity. The lowest exam grade you can get is Troll, below Dreadful.
There are also numerous occasions in the books where trolls are mocked for being lumbering, brainless beasts without much intelligence or sophistication.
“How could a troll get in?” Harry asked as they climbed the stairs.
“Don’t ask me, they’re supposed to be really stupid,” said Ron.
(Philosopher's Stone, Chapter 10, Halloween).
“Anyone can speak Troll,” said Fred dismissively. “All you have to do is point and grunt.”
(Goblet of Fire, Chapter 7, Bagman and Crouch).
“And that complete cow Pansy Parkinson,” said Hermione viciously. “How she got to be a prefect when she’s thicker than a concussed troll ...”
(Order of the Phoenix, Chapter 10, Luna Lovegood).
“You see what she’s up to? It’s her thing about half-breeds all over again - she’s trying to make out Hagrid’s some kind of dim-witted troll, just because he had a giantess for a mother..."
(Order of the Phoenix, Chapter 21, The Eye of the Snake).
Leaving aside Hermione's blatant troll prejudice here, it's pretty self-evident that troll=idiot.
Which makes it odd when Hermione (acting as Minister for Magic) decides to seek them out to help the Ministry in The Cursed Child.
HERMIONE: We haven’t given up. We’ve gone to the giants. The trolls. Everyone we can find. The Aurors are out flying, searching, talking to those who know secrets, following those who won’t reveal secrets.
(The Cursed Child, Act 4, Scene 1).
What possible indication could there have been that the trolls would a) entertain conversation or b) have any meaningful information for the Ministry? The fate of Barnabas the Barmy should surely be warning enough for any sane individual.
Furthermore, Aurors are highly trained magical spies. Neutralising angry trolls seems below their pay grade. Even if there was an emergency and Hermione was desperate it hardly seems like the best way of deploying her team.
Why did Hermione think that going to the trolls was going to be of any help whatsoever?