// the magic add a new tabpage at the end public override void ModifyTabPages(TabControl tabcontrol) { TabPage page = new TabPage(); page.Tag = tabcontrol.TabCount + 1; // at end used for undock/dock feature to define the order page.Text = "Multi Editor"; multieditor = new MultiEditor.MultiEditor() { Dock = DockStyle.Fill }; page.Controls.Add(multieditor); tabcontrol.TabPages.Add(page); }