Without the slightest doubt the (semi-) automated workflow that is of greatest value to me is the one I use to export diary entries from Day One into DEVONthink—and then, in DEVONthink, update the Day One links (i.e., cross-references to other diary entries) to DEVONthink links and convert Day One hastags to YAML front matter.
That uses Hazel, shell script and then (once in DEVONthink) DEVONthink smart rules and extensive AppleScript (plus Keyboard Maestro for an incredibly useful conflict palette).
The reason the workflow is so valuable to me is that it gives me the ability to journal using the Day One interface combined with the ability to use the phenomenal DEVONthink search facilities (which put Day One’s search facility in the shade). I use DEVONthink search several times every day to search my 50+ years of diary entries.
Stephen