Какие идиомы использовать в IELTS эссе

Использовать идиомы или нет? Список формальных идиом

Меня часто спрашивают:

Мария, у вас в Гайде по IELTS Writing для task 2 сказано не использовать идиомы, т.к. они неформальны, но в критериях lexical resource их использование наоборот приветствуется. 
Что же в итоге делать? 
Использовать идиомы или нет? 
Или может есть какие-то формальные идиомы? 

Есть! НО!

Обычно, в письменной части, идиомы не используем, т.к. график и эссе формальны.

В критерии Lexical Resource, один из пунктов на 7.0: There is some ability to use less common and/or idiomatic items.

На 8.0: There is skilful use of uncommon and/or idiomatic items when appropriate.

Т.е НЕ обязательно только idiomatic items.

Idiomatic items - это не только идиомы, но и фразовые глаголы тоже. 
On the one hand, ... / On the other hand, ... - идиомы нейтральные и подходят для эссе. To cut a long story short - нет.

Использовать идиомы или нет?

В writing - лучше нет, т.к. с идиомами легко ошибиться, и такие ошибки выглядят очень неестественно. Для письменной части, лучше использовать формальные фразовые глаголы. 

Тут список: 
https://yourielts.ru/prepare-for-ielts/ielts-writing/what-phrasal-verbs-to-use-in-ielts-writing

В устной части можно, но 1-3 идиомы за весь speaking. Лучше неформальные фразовые глаголы, т.к. они звучат намного естественее многих идиом и их легче использовать.

Список формальных идиом

Эти идиомы формальны и их можно использовать в IELTS эссе и академических текстах. Они позволяют нам кратко писать наши мысли и делают текст более выразительным.

On the one hand,
On the other hand,

in (the) light of
In the light of recent incidents, we are asking our customers to take particular care of their personal belongings.

in the hands of
A large percentage of the nation's wealth is in the hands of a very, very few people.

along the lines of
They're campaigning for the electoral system to be reformed along the lines of (= so that it becomes similar to) the one in Germany.

in its own right
This hospital is an advanced critical care center in its own right.

break new ground
This recovery technique breaks new ground.
This film broke ground for women's liberation.

the bottom line
The bottom line is that we need another ten thousand dollars to complete the project.

from scratch
Can we fix the current computer system, or would it be better to start from scratch with a new system?

state-of-the-art
a state-of-the-art computer

behind the scenes
A lot of hard work has been going on behind the scenes.

Across the board
The coronavirus has affected society across the board

Bear in mind 
Bearing in mind that many people are struggling to survive, this money should be redirected towards helping them with basic necessities. 

Driving force behind smth
The driving force behind Apple’s success was Steve Jobs.

Last resort
Asking them to leave the school should be a last resort.

Trial and error
Children learn by trial and error

Bridge the gap (Reduce the difference between two groups, concepts, or things)
This project bridges the gap between theoretical physics and engineering.

In the long run
Smoking feels good in the short run, but in the long run it can damage your health.

A means to an end (A way of achieving a goal)
Raising taxes is just a means to an end. 

Bring to Light (Reveal something previously unknown or hidden).
The study brings to light new data on the impact of air pollution on cognitive decline.

Set in Motion (Initiate or start a process)
The grant funding set in motion a series of experiments aimed at finding new antibiotics.

Strike a Balance (Find a compromise between two opposing elements)
The paper strikes a balance between theoretical discussion and practical application, making it accessible to both scholars and practitioners.

A Window of Opportunity (A period in which conditions are right for achieving something)
The rapid advances in renewable energy technology present a window of opportunity for governments to invest in sustainable infrastructure

Lay the groundwork (Provide the foundation for something to happen)
This study lays the groundwork for future research on urban sustainability by defining key metrics for success.

In the realm of (Within a particular field or area of study)
In the realm of neuroscience, this study examines the effects of sleep deprivation on cognitive function.

Give rise to (Cause something to happen or exist)
The emergence of new technologies has given rise to innovative approaches in the field of renewable energy.

Shed light on (Provide clarification or understanding about a particular topic)
This research sheds light on the impact of social media usage on mental health among adolescents.

Pave the way (Make progress or create conditions that will lead to something else)
This research paves the way for more accurate models of climate change.

Set the stage (Create the necessary conditions or context for something to happen)
This literature review sets the stage for future research by outlining the key debates in the field of environmental science.

Plant the seeds (Begin a process that will develop over time)
This preliminary study plants the seeds for a long-term investigation into the economic impact of renewable energy.

Reap the benefits (Enjoy the positive results of efforts)
By implementing sustainable farming practices, farmers can reap the benefits of increased crop yields.