Any note (but not agents, etc.) can be opened as a 'tear-off' stand-alone window. The window display the note's $Text and Displayed Attributes table. Both are editable and will update the source note in the main window. There is no title bar or HTML/Preview tab. Note that drag-drop or link-dragging between windows is not supported.
When a document is reopened, any 'tear-off' text windows that were open when the document was saved are also reopened. These text windows are moved in front of other windows lest they be hidden and forgotten.
The meaning of the styling of different rows in the Displayed Attributes table (bold, strikethrough, etc.) is explained here.