Currently when a letter is written in database view (from the "write a letter tab", it can be saved as an action and easily accessible in the actions tab in database view. However, in NXT the action appears but there is no way to access the letter that was written.
Not being able to view sent letters in NXT is a really bizarre gap in what is supposed to be a user-friendly interface - it's not user-friendly to have to switching between web and database view! This is why I only use database view, as I can't actually do my job in NXT. Other people in my team however, are starting to use NXT, but they can't fully do their jobs in NXT either.
This has been a policy of ours for years - we create ack letters directly from the gift record so that we can save the letter to the gift, allowing officers to access it immediately without having to go to our shared drive. Losing this capability with NXT is really disappointing.