Vassili Bykov has posted a nice modification to the Refactoring BRowser - I think I'll keep this one loaded:

VB-Sketch-DontModeMeIn is an attempt to fix that within the constraints of the existing RB and the UI framework.

Load it. Close any open browsers. Open a new one. Look at a method source. Start changing it. Without accepting, click on another method. Or another class. Or search for a class. The button with a red circle and white dots at the bottom of the browser is the link back to the postponed edit left behind. The same works for class comments or any other tools. For example, while writing a class comment you can have a peek at class methods to remember what that instance creation method was called.