The users will be doing a lot of drag/drop and there could be 10-15 appointments per day, so being able to see everything go makes the most sense. The row height should increace when containing more appointments and reduces its height if there are no appointments for that specific day.

Please refer to the attached sample project. When you start the application the form's text indicates how many times the AppointmentFormatting event is fired for only 30 appointments - more than 400 times. The more appointments you have , the more times the vent is initially fired,e.g. if you have 50 appointmens it is fired If you switch between the different views you will see how the counter increases its value.

Currently, only one resource can be printed on a single page. It should be possible to print the appointments for more than one resource on a single page, just like RadScheduler allows you to set the number of resources per view.

Currently RadScheduler can only group the appointments first by resource and then by date. It should be possible to group the appointments in day view and in week view first by date and then by resource.

To reproduce:
        Me.RadScheduler1.ActiveViewType = Telerik.WinControls.UI.SchedulerViewType.Timeline
        Dim timelineView As SchedulerTimelineView = Me.RadScheduler1.GetTimelineView()
        Dim currentScaling As SchedulerTimescale = timelineView.GetScaling()
        currentScaling.DisplayedCellsCount = 100

Try to scroll horizontally. Then, change the currentScaling.DisplayedCellsCount  property to 50 and try to scroll again. You will notice a considerable difference.

Workaround: reduce the number of the displayed visual cell elements by the DisplayedCellsCount.

This request is to add Working hours range of the view, which will style the cells as working and non working. In addition, add a property ShowWorkingHours while will determine whether non-working hours are visible or not.

Or perhaps for the sake of consistency, we can have API as in the day view:
dayView.RangeFactor = ScaleRange.QuarterHour
dayView.RulerStartScale = 9
dayView.RulerStartScaleMinutes = 30
dayView.RulerEndScale = 14
dayView.RulerEndScaleMinutes = 45

To reproduce:
 public Form1()
 {
     InitializeComponent();

     for (int i = 0; i < 7; i++)
     {
         this.radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddHours(i),TimeSpan.FromHours(3),"App" + i));
     }
     this.radScheduler1.AutoSizeAppointments = true;
     this.radScheduler1.ActiveViewType = SchedulerViewType.Month;
     SchedulerMonthView monthView = this.radScheduler1.GetMonthView();
    
     monthView.EnableAppointmentsScrolling = true;
 }

Workaround: set the AutoSizeAppointments property to false.

To reproduce:

Color[] colors = new Color[]
{
    Color.LightBlue, Color.LightGreen, Color.LightYellow,
    Color.Red, Color.Orange, Color.Pink, Color.Purple, Color.Peru, Color.PowderBlue
};
Random rand = new Random();
for (int i = 0; i < 25; i++)
{
    Resource resource = new Resource();
    resource.Id = new EventId(i);
    resource.Name = i + ".Resource";
    resource.Color = colors[rand.Next(0, colors.Length)];
    this.radScheduler1.Resources.Add(resource);
}

this.radScheduler1.GroupType = GroupType.Resource;
this.radScheduler1.ActiveView.ResourcesPerView = this.radScheduler1.Resources.Count;

for (int i = 0; i < 3; i++)
{
    Appointment a = new Appointment(DateTime.Now.AddHours(i), TimeSpan.FromMinutes(30), "A" + i);
    a.ResourceId = this.radScheduler1.Resources.Last().Id;
    this.radScheduler1.Appointments.Add(a);
}

NOTE: it is also valid for the horizontal scrollbar in Timeline view.

Workaround: use the SetResourceSize to increase the last resource's width a little bit: http://docs.telerik.com/devtools/winforms/scheduler/views/grouping-by-resources

It should be possible to set the step of the ruler in Day/Week view to two or more hours.

It would be nice if the RadScheduler allows dragging of multiple selected appointments and change the events'  start time in correspondence with the active appointment offset time.

Please refer to the attached screenshot from Outlook.

To reproduce:
this.radScheduler1.RightToLeft = System.Windows.Forms.RightToLeft.Yes;
this.radScheduler1.Appointments.Add(new Appointment(DateTime.Now, TimeSpan.FromHours(2), "آقای حقیقت"));

Please refer to the attached screenshot.

Workaround:

private void radScheduler1_AppointmentFormatting(object sender, SchedulerAppointmentEventArgs e)
{ 
    e.AppointmentElement.UseHtml = false; 
}

Filtering should not show the appointments which have their resources not visible.

The functionality provided by the EditRecurrenceDialog should also be available in a user control. This would allow the users to embed it in their applications.

Add the possibility to have multiple time intervals on the DayView's display range.

Currently RadScheduler does not support binding to DataView objects.

Run the application on a Windows 10 machine and scroll to the bottom. Please refer to the attached gif file.