BorderGroup:

gistfile1.txt

    public class BorderGroup
    {
        private static Vector2 _startPos;
        private static Vector2 _labelSize;
        private static uint _colour;
        public static void BeginBorder(string label, uint colour)
        {
            ImGui.PushID(label);
            _colour = colour;
            _startPos = ImGui.GetCursorScreenPos();
            _startPos.X -= 3;
            _startPos.Y += ImGui.GetTextLineHeight() * 0.5f;
            ImGui.Text(label);
            _labelSize = ImGui.GetItemRectSize();
        }

        public static void BeginBorder(string label)
        {
            BeginBorder(label, ImGui.GetColorU32(ImGuiCol.Border)); 
        }
        
        public static void BeginBorder(string label, ImGuiCol colorIdx)
        {
            BeginBorder(label, ImGui.GetColorU32(colorIdx)); 
        }

        public static void EndBoarder()
        { 
            Vector2 size = new Vector2(ImGui.GetContentRegionAvail().X, ImGui.GetCursorScreenPos().Y - _startPos.Y);
            //ImGui.get
            ImDrawListPtr wdl = ImGui.GetWindowDrawList();

            Vector2[] pts = new Vector2[6];
            pts[0] = new Vector2(_startPos.X + 2, _startPos.Y);
            pts[1] = _startPos; //top left
            pts[2] = new Vector2(_startPos.X, _startPos.Y + size.Y); //bottom left
            pts[3] = new Vector2(_startPos.X + size.X + 3, _startPos.Y + size.Y); //bottom right
            pts[4] = new Vector2(_startPos.X + size.X + 3, _startPos.Y);
            pts[5] = new Vector2(_startPos.X + _labelSize.X + 3, _startPos.Y);
            wdl.AddPolyline(ref pts[0], pts.Length, _colour, false, 1.0f);
            ImGui.PopID();

        }
    }