Mikolaj, take a look at this topic:
Here is a workflow for building Json String based on dictionaries.
I use it to build a body for Jira API.
As Maciej mention check out his guide on how to start creating APIs for Orchestrator based on the Swagger documentation.
I started my adventure with API at the beginning of this year from the same topic.
Anil_G
jast1631
donghai
gulsheen_kaur1