<p>When using tooltips to show a detailed description of a TreeNode, the tooltip is drawn on top of the node, as if it was completing the node's text. Also, if the text is long, the tooltip is positioned in a way that the <strong>text exceeds the screen</strong>. </p>

<p>But what I need is the tooltip to show right below the mouse pointer and not on top of the TreeNode.</p>

<p>Any idea how to do this?</p>

<hr>

<p>Show, don't tell:</p>

<p>How it is:  </p>

<p><a href="https://i.stack.imgur.com/aqDww.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aqDww.png" alt="how it is"></a>
  </p>

<p>How I want:  </p>

<p><a href="https://i.stack.imgur.com/buIrV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/buIrV.png" alt="how I want"></a>
</p>

You need to define a ToolTip and write an MouseOverEventHandler for the TreeView. In the MouseOverEventHandler calculate the node above which mouse is positioned, then show the description ToolTip. Also make sure you are not setting the tooltip description more than once, otherwise the behavior is quite ugly.
A better way is to show the description in the StatusStrip - bottom left of the Form.
Update:
OK since you have clarified your question. You can use
```
ToolTip.Show
```
method where you can specify coordinates:
```
```
public void Show(
    string text,
    IWin32Window window,
    int x,
    int y,
    int duration
)
```
```
Obviously, you'll have to add offset to x and y.