It would be very helpful to be able to add a person access to the file/task, but as it is private.

Example:

1) There is a legal department where each task is private for each lawyer, but there are people who report these documents and, for example, after custom fields add these people so that they do not see other files of other people where there is private data.

2) HR department: limit the visibility of tasks where there are private contracts etc to assignee people where e.g. there are people you hire, so each person in the company has their task where are contracts etc and only that person+HR has access