Hi!
version 7.1
So, I came here looking for help, struggling with finding the summary block myself - but I just figured it out!
On your homepage or wherever you want the summary to be:
1. click to add 'new section'
2. click the top one - 'add blank +'
3. hover over and tap the blue '+' on the line
4. you'll find the summary block down at the bottom, between markdown and social links.
5. select the page you want the summary from (I can only add blog pages but that may differ for you?) and change all the settings you want
Some of you may already have said it, but I thought to just make it super clear for everyone wondering exactly how to do it.