Account master users can allow user managers to manage shared question library folders.
This is acheived via an option that is set for all user managers.
Activating User Manager Shared Question Library Management
To activate Question library management for User Managers, navigate to the “User Management” section of your account by choosing it from the “Account” drop-down in the top nav bar.
On the user management page, in the upper-right of the table that lists the users on the account, there’s a grey button, next to the search box. Click this button.
With the settings box open, click the toggle next to "Allow user managers to manage shared question library folders" to On.
With this setting active, the user managers will have the same level of control over the shared question library folders as the master user.