One of the requests we've long had is for a spell-checker in User Note and User Tool Edit windows. This feature has now been added in the 7.1 update.
To use this feature, you must first have an Edit window active, then choose Spelling... from the Search menu (or use the keyboard shortcut shift-command-semicolon). The following window will then appear:
The first occurrence of a questionable word will be highlighted and suggested replacements given. You can double-click one of the suggested replacements to insert it into the text in place of the misspelled word, or you can type in a replacement and hit return. If the word is correct, you can click the Find Next button to move to the next misspelling, or Skip to ignore any future occurrences of that word. If you want to Correct All instances of a misspelling, use the Correct All button. Finally, the Learn button adds the questionable word to the OS X spelling dictionary so that the word will no longer be flagged in future spell-checks.