import os

def create_text_file(filename, content, directory=""):
    """Create a text file with the given content."""
    if directory and not os.path.exists(directory):
        os.makedirs(directory)
    with open(os.path.join(directory, filename), 'w') as file:
        file.write(content)

def save_text_file(filename, content, directory=""):
    """Save content to a text file."""
    create_text_file(filename, content, directory)

def read_all_text_files_in_folder(directory):
    """Read and return the content of all text files in the specified folder."""
    contents = []
    for filename in os.listdir(directory):
        if filename.endswith(".txt"):
            with open(os.path.join(directory, filename), 'r') as file:
                contents.append(file.read())
    return contents

def append_to_text_file(filename, content, directory=""):
    """Append content to an existing text file."""
    with open(os.path.join(directory, filename), 'a') as file:
        file.write(content)