An easy to work with jump in Godot

better_jumping_character_example.gd

extends KinematicBody2D

export var move_speed = 200.0

var velocity := Vector2.ZERO

export var jump_height : float
export var jump_time_to_peak : float
export var jump_time_to_descent : float

onready var jump_velocity : float = ((2.0 * jump_height) / jump_time_to_peak) * -1.0
onready var jump_gravity : float = ((-2.0 * jump_height) / (jump_time_to_peak * jump_time_to_peak)) * -1.0
onready var fall_gravity : float = ((-2.0 * jump_height) / (jump_time_to_descent * jump_time_to_descent)) * -1.0

func _physics_process(delta):
	velocity.y += get_gravity() * delta
	velocity.x = get_input_velocity() * move_speed
	
	if Input.is_action_just_pressed("jump") and is_on_floor():
		jump()
	
	velocity = move_and_slide(velocity, Vector2.UP)

func get_gravity() -> float:
	return jump_gravity if velocity.y < 0.0 else fall_gravity

func jump():
	velocity.y = jump_velocity

func get_input_velocity() -> float:
	var horizontal := 0.0
	
	if Input.is_action_pressed("left"):
		horizontal -= 1.0
	if Input.is_action_pressed("right"):
		horizontal += 1.0
	
	return horizontal

Just commenting to confirm, this code does work on Godot 4.6.3. However, a few keywords were removed moving into Godot 4. The errors will prompt you to just change all of the "onready" and "export" statements so they start with "@" I also added the following bit of code to this.

if Input.is_action_just_released("jump") and velocity.y
# Decrease Jump Velocity
velocity.y *= _jump_cut_off_value

Add a var to so it works correctly: "_var _jump_cut_off_value : float = 0.4"