This sub-menu of the Edit menu, contains the following items (all items except first require text pane focus):
- Show/Hide Spelling and Grammar. Toggles the OS Spelling and Grammar dialog.
- Check Document Now. This causes any items not matching the host OS' spelling list to be underlined in red.
- Check Spelling While Typing. Clicking this causes "Check spelling" to permanently turned on. The item acts as an on/off toggle (default = off). When turned 'on' a tick is shown in the left margin of the menu. This is set (per file?) on this menu. There is no preference setting. This can be set in the General tab of Document Settings. Individual notes can be excluded from setting their $NoSpelling attribute to 'true'. The text pane respects the Document settings' checkbox "check spelling at you type": if a note is selected, and if the note uses the default value of $NoSpelling, changing this setting immediately updates spell checking for that note.
- Check Grammar with Spelling. Turns on grammar error detection alongside spelling prompts.
- Correct Spelling Automatically. Tinderbox will automatically correct any spelling mistakes it detects.
If you need to choose/alter the language used for spell-checking, open OS System Preferences, Language & Text preferences, Text tab. The latter's "Automatic by Language" option for Spelling, seems to work contextually at around sentence scope.