Hi Folks!
New around these parts, so apologies if this isn’t the right place for this. It felt like the most suitable home.
I created a brief script for additive 2d camera shake (when you have multiple shakes overlapping and you want them to combine to extend the shake and increase it’s magnitude) that I wanted to share so someone looking for it in the future might find it. Hopefully this is helpful for someone! 
class_name ShakeableCamera extends Camera2D
var shaking := false
var remaining_time : float = 0
var elapsed_time : float = 0
#strength controlls the overall magnitude of the shake
#while smoothness controlls how smooth motion is, kind of "anti-strength"
var smoothness :float = 0.5 #0-1, higher values smooth out the shake motion more so that it's less jarring
var current_strength :float = 0
func rand_offset_from_strength()-> Vector2:
var vec = Vector2()
vec.x = randf_range(-current_strength, current_strength)
vec.y = randf_range(-current_strength, current_strength)
return vec
func shake(time:float, strength: float):
#If the camera is already shaking, then
#reset the elapsed time and remaining time of the shake
#boost the strength of the shake, so that shakes have an additive effect
remaining_time = time
current_strength += strength
elapsed_time = 0.0
var offset_position := Vector2(0,0)
var offset_rotation = 0
#If shakes overlap, any subsequent call only effects the shake by changing
#the variables. The first call handles the actual shaking.
if not shaking:
shaking = true
while elapsed_time < remaining_time:
#gradually decay the strength
current_strength = lerpf(current_strength, 0, elapsed_time/remaining_time)
#smooth motion in the offset between random values
offset_position = offset_position.lerp(rand_offset_from_strength(), 1-smoothness)
#lerp back towards zero offset over time
offset_position = offset_position.lerp(Vector2(0,0), elapsed_time/remaining_time)
offset = offset_position
#if you want to add rotation to the shake, uncomment the line below
#rotation = lerpf(randf_range(deg_to_rad(0),deg_to_rad(0)),0, elapsed_time/remaining_time)
elapsed_time += get_process_delta_time()
await get_tree().process_frame
shaking = false