In Messages, to create a new message tap the pencil-in-a-square icon in the upper right corner.
In Notes, to create a new Note, tap the pencil-in-a-square icon in the lower right corner.
In Calendar, to create a new appointment, tap the + icon in the upper right corner.
In Reminders, to create a new reminder, tap the + in a blue circle in the lower left corner. At least it offers a text label "New Reminder"
These are all Apple apps and they all do it differently. And that's not even getting into gestures and other actions that you just have to stumble upon to even know they exist.
Consistency has been on the decline within Apple apps for sure, but it gets much worse after introducing cross platform apps into the mix.
The main one I end up missing most is the swipe to go back gesture within apps. It comes for “free” when using UIKit and SwiftUI navigation primitives (UINavigationController, UISplitViewController, and their SwiftUI counterparts) but it’s almost always missing from apps built with React Native and such.