Why Postman.setPreviousRequest() not exist?

Help
#1

I have a collection with invalid scenarios, to simulate bad request about required fields.
But before to send my request I need generate a number_token.

Collection Ex.:
Post token card >> generate a number_token to next request
Post save card, using valid number_token above, but without field experation_month

Post token card >> generate a number_token to next request
Post save card, using valid number_token above, but without field experation_year

Post token card >> generate a number_token to next request
Post save card, using valid number_token above, but without field cardholder_name

There’s a way to set a “Previous Request”, in Pre-request Script, that no need repeat the request to generate a number_token?

Ex.:
Post token card >> generate a number_token to next request
Post save card, using valid number_token above, but without field experation_month
Post save card, using valid number_token above, but without field experation_year
Post save card, using valid number_token above, but without field cardholder_name

#2

If I understand correctly, you’d like to make the same request before running every request in a collection.

You could add a Pre-request script to your entire collection:
https://learning.getpostman.com/docs/postman/scripts/pre_request_scripts/#adding-a-pre-request-script-to-a-collection-or-folder

In your Pre-request script you can use pm.sendRequest to generate your token and save it in a variable ready for when the request runs:
https://learning.getpostman.com/docs/postman/scripts/postman_sandbox_api_reference/#pmsendrequest