app.py

import streamlit as st
from streamlit_option_menu import streamlit_option_menu

# Create a nested streamlit-option-menu
options = [
    "Option 1",
    streamlit_option_menu(
        "Sub Menu",
        options=["Option 2", "Option 3"],
        default="Option 2",
        style={"width": "100%"},
    ),
]

# Display the streamlit-option-menu
streamlit_option_menu("Main Menu", options, default="Option 1", style={"width": "100%"})