David Anderson sometimes provides an overview of updates as part of Quick Tips (Watch Storyline 360 Webinars - Articulate 360 Training). Unfortunately, you'll have to check the topics for each recording to find where those are.
You could just go through the areas of the Player, as well as the ribbons, and see what you recognize and what you don't. (That's actually a good way to discover functionality that's been around but tends to be overlooked.)
Otherwise, I suggest you simply challenge yourself to do something in Storyline and then see if you can figure out how to do it.
Best wishes as you get back up to speed!
Thanks! Little from Col A little from Col B. Actually had TWO .onenotes on Version History so combo'd those, and sorted by topics (ux/ui, triggers, states, accessibility, quizzing, 360 Images, ...), and then start (weed) wacking!
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