We can create a Scrollable menu panel with buttons at the top and bottom to move the items. A similar functionality is already implemented in WPF:

The default MS ContextMenuStrip shows tooltips for disabled menu items:

Use the following code:

        public RadForm1()
        {
            InitializeComponent();
            this.IsMdiContainer = true;

            RadForm form = new RadForm();
            form.Text = "Net Core WinForms MDI Child 1";
            form.MdiParent = this; 
            form.Show();

            form = new RadForm();
            form.Text = "Net Core WinForms MDI Child 2";
            form.MdiParent = this; 
            form.Show();

            form = new RadForm();
            form.Text = "Net Core WinForms MDI Child 3";
            form.MdiParent = this;
            form.Show();

            this.radMenuItem1.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.X));
            this.radMenuItem1.Click += RadMenuItem1_Click;

            this.radMenuItem2.Shortcuts.Add(new RadShortcut(Keys.Control, Keys.A));
            this.radMenuItem2.Click += RadMenuItem2_Click;
        }

        private void RadMenuItem1_Click(object sender, EventArgs e)
        {
            RadMessageBox.Show("Ctrl+X");
        }

        private void RadMenuItem2_Click(object sender, EventArgs e)
        {
            RadMessageBox.Show("Ctrl+A");
        }

Expected result: Press Ctrl+X >> the respective message box is shown

Actual result: the message box is missing. Only when the MDI child forms are missing MDIParent, the shortcut is executed.

I noticed when you open a RadMenu in design view on a form where you want e.g. add some menu items, and, while the menu is open, you click on another form (e.g. to check on the items you created up there), the menu remains open, even if you navigate through other open windows in VS.

It took me a while to find out which menu I initially clicked on.

Please note, this happens sometimes, I did not find one way I can always reproduce this behavior.

After a few clicks I managed to close the menu...

It is a minor issue.

There is a MDI parent RadForm containing a RadMenu with items. There is a MDI child RadForm which also contains a RadMenu with items. The mnemonics are enabled for all the menu items. The menu merging is disabled (RadMenu.AllowMerge=false).

When you show the parent form together with the child form and focus the child form, pressing the Alt key highlights only the menu items from the parent form. It is not possible to activate the menu items from the child form.

Please refer to the attached sample project and gif file illustrating the obtained incorrect behavior and the observed behavior with a standard MS Form and MenuStrip