"Her natural patience has been useful in her work."
Translation:Sa patience naturelle a été utile dans son travail.
I agree - French prepositions send me screaming to a reference site! ☺
A couple of good ones are:
All beautifully summarised by Celine1988 here:
In short, they are used in many instances, but the one that interests us in regards to this sentence is:
En can mean in or to when followed directly by a noun that doesn't need an article:
Vous allez en prison ! - You're going to prison!
Il est en classe. - He's in school.
Dans means in a location when followed by an article plus noun:
Il est dans la maison. - He's in the house.
Qu'est-ce qui est dans la boîte ? - What's in the box?
I did some research and found that the article can be replaced by a possessive adjective. Example:
bloquer une date dans son agenda
put a date in your diary, reserve a date in your datebook
For further reading see: https://www.wordreference.com/fren/dans%20son
As they are prepositions, I'm sorry to tell you that there is no rule. However, keep in mind that en is only used in fixed expression en prison, en voyage, whereas dans = in in general. My advice would be to systematically use dans, and when you get corrected, learn the expression with en.
"Has been" can indeed imply up to the present, but it can also imply something in the recent past that is now completed. "He has been watering the flowers." (He may not be doing it right now, but he was recently as evidenced by the wet plants. "She has been instrumental in the completion of this project." (Project is now finished and she played an important role.)