Hide particular fields (not custom) of the tasks

[Aida Selimova]

 Situation
There are 2 projects: Project A and Project B (tasks from project A visible to the group of users with particular Security Level, this group is for externals added as team members)

The goal
Hide particular fields (not custom) of the tasks of project A in Project B. Investigating similar situations I undesrtood that there wiil be no solution from Atlassian team, even for Server, so no dreaming about solution for Cloud. From the other side there is no credible plugins in Cloud in marketplace for this.

What I tried
1. Cloned screens for Project B leaving only the fields that could be shown --> fail, because I understood that these screens will work only for tasks created inside the Project B.
2. Tried to play with Field configuration --> fail, same story

I´m thinking about
1. probably create an automation rule to move the tasks from Project A that neede to be shown to Project B, so all the configurations of Project B will be applied, although I want these tasks to be visible for the team in Project A with all fields (smth that needs to be sacrificed)
2. Hide the fields in Project A (same sacrification) 
3. Listen to your ideas if you have some, please :)

[Nic Brough -Adaptavist-]

I am not sure that I understand the requirement here, but it sounds like you want to show some data from issues to people who can't see the issues.  

Field level security (which Jira doesn't do anyway) would not help you with that - the users, by definition of the security should not be seeing the issues at all, let alone only bits of them.

Your only option is to copy the data to somewhere that the users can see it.  Or, better and more simple, stop hiding the issues from people who need to see them.