We have the same issue.As a large organization divided into countries we use BU's in Sales to limit visibility and here Parent/child works fine.Now we are using marketing App as well, and we have Marketing BU on top of Country BU's as we don't want Marketing leads and contacts to be shown pre-mature to sales.Issue with this setup is that we cannot use BU scope in Marketing app, as the parent/child BU scope is NOT available in Marketing app.So in order to do marketing to existing customers in Country, we need to have Marketing a Organizational Scope, meaning Marketing BU's have access to ALL contacts (also from other countries BUs).If we were to use BU Scope in Marketing app, Marketing would only see those owned by the Marketing BU (hence no existing contacts).The result is that Segmentation has to made with filters to limit to own country contacts and be checked and double checked as failure to do correct would hit wrong. And that may slip.Our Marketing users are used to working with Sales so they expect that the BU setup in Sales are the same in Marketing App - and again why should they not. It is Dynamics, and it is a seamless user experience - so they tend to take this understanding of the BU setup in Sales on to Marketing app.----------We would really appreciate that BU usage and options on scoping in Marketing app would include Parent/child setup.And that aligning Marketing App and Sales in terms of all BU Scope settings.