Frames with red borders in the Character and Word Dictionary windows are editable; you can change their contents.
To try this out in the Character Dictionary window, first make sure a character entry is displayed. Editable fields will not respond to keyboard input when no character entry is displayed. Next, click in the Notes field of the Character Dictionary window. Type something relevant to the currently displayed character. Whatever you enter here will be saved when you quit the program, and it will appear the next time you view the same dictionary entry. Notes are also searchable via the Search window.