I'm talking about a standard feature in MS Project which allows to collapse tasks at multiple Indent levels. It's called Outlining Tasks.It works something like this:When you select Outlining Level 1 - All the Tasks at Level 1 Indent will collapseWhen you select Outlining Level 2 - All the Tasks at ...

Not 100% sure, but I believe person B doesn't have view/manage permissions on tasks that are greyed out.