How to extract JSON data where key contains specual characters like dot or square brackets?

How to extract JSON data where key contains specual characters like dot or square brackets?

Hi,
I integrate form data from WIX.com and therefor cannot modify the original JSON names. I have to handle JSON-keys like:
- contact.Name.First
- contact.Email[0]

the standard access like ${webtrigger.payloca.data.contact.Name.First} or ${webtrigger.payloca.data.contact.Email[0]} does not access the data at.

Any ideas or help on this?
Many thanks!
Gerald