Hi Laura,
I’ve struggled with this new interface myself. Hopefully the below steps help.
On the Menu - click on Calendar - do not click on your listing to open the full calendar as it was before, just leave it as a strip, to only see the dates displayed in a row. I know it’s not easier than it used to be, but it seems to be the new version :(.
Then, when you click on a certain date from the strip calendar, on the right side of the screen there is a small arrow to expand another menu (if not already open in the right side). This menu on the right side should contain the old rules that you used to have regarding minimum night stays and it also allows you to create new rules to be applied further.
Coming back to when you’ve selected one certain date from the strip calendar, go in that right menu scroll all the way down until you find “Rule-sets” box. From there, you can choose your minimum stay rule. Hope this helps. By the way, I hate the new version of the calendar…
I already left a feedback with Airbnb, hopefully it will matter and more of us will do that if they are unhappy as we are.
Have a great day,
Andreea