Key Press Behaviors
Summary
The most basic of behaviors, is the ability to send certain keycode presses and releases in response to activating a certain key.
The categories of supported codes are:
Please visit the codes section for a comprehensive list.
For advanced users, user-defined HID usages are also supported but must be encoded, please see dt-bindings/zmk/keys.h for further insight.
Keycode Defines
To make it easier to encode the HID keycode numeric values, most keymaps include
the dt-bindings/zmk/keys.h header
provided by ZMK near the top:
#include <dt-bindings/zmk/keys.h>
Doing so makes a set of defines such as A, N1, etc. available for use with these behaviors
Key Press
The "key press" behavior sends standard keycodes on press/release.
Behavior Binding
- Reference: 
&kp - Parameter: The keycode usage ID from the usage page, e.g. 
N4orA 
Example:
&kp A