As mentioned in the title, we want to change the visibility of a section (main_section1) in a form of a custom entity (new_main) based on both, a value in an option field in a related entity (new_related1, is related 1:N tonew_main by lookup field new_related1id) and a value of a lookup field in another related entity (new_related2, is related 1:N to new_main by lookup field new_related2id).
The thing is, I know how to change the visibility of fields and sections based on field values in the same entity but I don't know how to get data from fields in another entity.
While getting square eyes from googling this matter I found some posts mentioning JSON and REST. I'm unfamiliar to this, and I couldn't find out how to implement this at my organization.
I can use a workflow to fill a value of a hidden field based on the the values in the two related entities, so I have all the information I need in one entity so I don't have to use script to look into another entity. But that is my last hope, I'd rather fix this solely with javascript.
I hope you can give me some tips to help me out to solve this thing. If JSON and/or REST is needed for the solution, I hope you can also give me some tips on how to use it.
Thanks!