Ensure that the folder parameter is not empty by adding a valid attribute.

Examples:

New-MgDriveItem -DriveId $Global:driveId -BodyParameter @{
    name = "TestFolder"
    folder = @{ "@odata.type" = "microsoft.graph.folder" }
}

New-MgDriveItem -DriveId $Global:driveId -BodyParameter @{
    name = "TestFolder"
    folder = @{ "childCount" = 1024 }
}

Why This Works

Microsoft Graph PowerShell requires at least one non-empty property inside folder = @{} to properly register the request.