If I make all GridItems invisible, then the plus sign remains in RadPropertyGrid for Font item.

Example:

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            Make();
        }

        private void Make()
        {
            radPropertyGrid1.SelectedObject = new Item();
            foreach (var item in radPropertyGrid1.Items)
            {
                if (!(item.Value is Font)) continue;
                foreach (var subItem in item.GridItems)
                {
                    subItem.Visible = false;
                }
            }
        }

        public class Item
        {
            [DisplayName("Font"), Category("Font")]
            public Font Id { get; set; }

            public Item()
            {
                Id = new Font("Arial", 12, FontStyle.Regular);
            }
        }

    }

if I modify my procedure Make() and add

       radPropertyGrid1.ExpandAllGridItems();
at the end, then when you change the font (or reset), all hidden topics reappear

Full text:

        private void Make()
        {
            radPropertyGrid1.SelectedObject = new Item();
            foreach (var item in radPropertyGrid1.Items)
            {
                if (!(item.Value is Font)) continue;
                foreach (var subItem in item.GridItems)
                {
                    subItem.Visible = false;
                }
            }
            radPropertyGrid1.ExpandAllGridItems();
        }

I need ExpandAllGridItems, because the object in the radPropertyGrid is actually very complex and contains many properties

As you advised, I added two events for radpropertygrid:

        private void radProperty_ItemExpandedChanging(object sender, RadPropertyGridCancelEventArgs e)
        {
            if (e.Item is PropertyGridItem item && item.Value is Font)
            {
                e.Cancel = true;
            }
        }
        private void radProperty_ItemFormatting(object sender, PropertyGridItemFormattingEventArgs e)
        {

            if (e.Item is PropertyGridItem itemF && itemF.Value is Font)
            {
                if (e.VisualElement is PropertyGridItemElement el) el.ExpanderElement.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;
            }
        }

Everything works correctly. But as soon as I start to scroll through the contents, there are visual artifacts.

In the beginning, I scroll down until the upper elements disappear. Then scroll up to see the top elements.

Notice where the "Size" and "Value" are now drawn. 

If you scroll through the contents again, some of the elements are randomly and unpredictably drawn in the wrong place.

The first approach still has an artifact: "font" is shifted to the left.

Second approach solved all the problems.