How would I add a cheat code to a title screen

Raptorkillz That addon works with keys, not with actions.
I wrote you the complete thing. Just connect the signal and do whatever you want (play sound etc...) in the signal handling function. If you don't understand what I'm talking about, you really need to go through the introductory tutorial I mentioned earlier.

Raptorkillz Of course it isn't because you're connecting the signal after it's been emitted. You need to do it beforehand. Put the connect call in _ready() or connect it manually in the inspector.

Raptorkillz Use a simpler cheat code for testing and put a print statement in the signal handler to see it it's getting called. Also make sure you don't have multiple actions mapped to the same input because the script will use only the first mapped action it finds in the InputMap.
Btw you have too much whitespace in your code.

Raptorkillz func _input(e):
for a in InputMap.get_actions().filter(func(aa): return e.is_action_pressed(aa)).slice(0,1):
s += a if not s else " " + a
for k in cheats.keys(): if s.contains(k): code_entered.emit(cheats[k]); s = ""

is this function even correct?

im not fond of lambdas because its convoluted.

i dont like this line:

s += a if not s else " " + a

Seems like if s - the entered cheat sequence is nothing/empty then you start new sequence with " " a space at the beninging. So it will never match the cheat or i maybe wrong here?

also the last line

for k in cheats.keys(): if s.contains(k): code_entered.emit(cheats[k]); s = ""

does ; at the end or signal.emit() means if condition fails then do - s = ""??

kuligs2 is this function even correct?

It is. I wrote it. In a compacted tabletdev style

Raptorkillz Use a trivial test example.

• use actions you know 100% are defined and map 1:1 to physical input, because you might have messed up something with your action definitions
• use trivial sequence to speed up your testing, because you're testing how the parts of your code are communicating so the actual sequence is not important
• print immediately at the start of the signal handler
• print the sequence as it builds up
• double check your signal connections
• be sure to catch and understand all error messages the engine might be reporting
• If you can't use print() on your dev platform - use a different platform or set things up in a way so you can see your prints. Developing without printing is not a very wise thing to do. It just makes tracking the flow of your code needlessly more difficult.

class_name CheatCodeCapture extends Node
signal cheat_code_entered(name: String)
var s: String
var cheats: Dictionary = {"ui_left ui_right" : "cheat1"}

func _input(e):
	for a in InputMap.get_actions().filter(func(aa): return e.is_action_pressed(aa)).slice(0,1):
		s += a if not s else " " + a 
		print("current sequence: ", s) # debug
		for k in cheats.keys(): if s.contains(k): cheat_code_entered.emit(cheats[k]); s = ""

func _ready():
	cheat_code_entered.connect(on_cheat)
	
func on_cheat(name):
	print(name) # debug

kuligs2 Here's an "educational" version for easier understanding:

class_name CheatCodeCapture extends Node
signal cheat_code_entered(name: String)
var action_sequence: String
var cheatcodes: Dictionary = {"ui_left ui_right" : "cheat1"}

func _input(event):
	# iterate through actions defined in input map
	for action in InputMap.get_actions():
		if event.is_action_pressed(action):
			# accumulate actions
			if not action_sequence.is_empty():
				action_sequence += " " # insert space between actions
			action_sequence += action
			# check if the current action sequence is present in any of cheatcodes
			for code in cheatcodes.keys():
				if action_sequence.contains(code):
					# action sequence found, emit the signal and clear the accumulated sequence
					cheat_code_entered.emit(cheatcodes[code])
					action_sequence = ""
			break