Always look to last year for the organizer. Click the organizer just to the right of the proform (18 -> 19) icon. There really is no default organizer, just some text to help with formatting. All of the options are there, most setup is when you click Print Paper Organizer.
There isn't a *default* engagement letter per se; you have to type in your own verbiage.
It's in the organizer settings; you start in 2018 software to generate organizers:
Tools > Organizer > Engagement Letter then start typing. Beware that the word processor used by Lacerte is marginal (at best....) You can try typing up your letter in Word, then cut/paste/modify.
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