We have LLM memory, it's a training data from which the model was initially programmed. To allow adding or changing LLM memory, we would need to retrain model completely or partially. And that is not realistic any time soon. All other attempts at LLM memory would be just an obscure hack of splitting context window into parts and feeding input from different files. Literally nothing would change if you input half of the query from one file, half from another called "memory.txt" or if you just input whole query from a single file twice as big.