If the note node will be a ShapeNode, then indeed its Shape property will be initialized from DefaultShape when drawing with the mouse. Alternatively, you can set property values for interactively drawn nodes from the InitializeNode event - it is raised just before the user sees the new node.

1) change the color

Set node.Brush;

2) add shadow effect

Set node.Effect = new DropShadowEffect();

3) make it editable

If you enable AllowInplaceEdit, you can edit node's text by double clicking. Alternatively, you could call the BeginEdit method from NodeClicked event if you prefer single-click edit.

4) maybe multiple editable regions like a header/contents

You could use a TableNode and show text in its Caption area and cells.

5) make it collapsible?

If you mean collapsing a tree branch rooted at that node, set the node.Expandable property to display a +/- icon for expand / collapse. If you mean the node's content should collapse/expand, you could for example set table's Bounds.Height = table.CaptionHeight to collapse the content in response to NodeClicked events.

I hope that helps,
Stoyan