You can create a widget stack of up to 10 widgets with the Smart Stacks feature. Introduced with iOS 14, it allows you to stack (put one above the other) 10 widgets on top of each other.
Why its called smart, as it surfaces particular information based on the time of day and how a user uses his phone. Say, music app on top when you are exercising and showing calendar appointments at the start of the day.
To do this, first long press and hold on to an empty space on your home screen to enter into ‘edit’ mode. Now, drag one widget over another to create a stack. Once the stack is created, you can drag more widgets over the stack to add. Tap ‘Done’ at the upper right corner when you are done.