How do I add multiple cities to the weather widget? As it was before.

i need to add, you now need to use individual widgets for each location. you can no longer have multiple locations in one widget.

Tell Apple what missing features you'd like restored or new features added to the system via Feedback - macOS - Apple.  

all you need to do is open "edit widgets"

and then add as many cities as you want by clicking the green "add" button.

then manually change the location for each of the added forecast widgets.