A session begins when we send the command:
streamlit run app.py
And open the browser on the given url.
To create a new or second session, just open another tab or window with the given url.
You can use session state to manage what you want inside a single session. If task 1 processes web scraping and task 2 is doing some regression analysis you can do so. Just manage the variables in the session states so that the app may run without issues even if there are possible code reruns. Talking about reruns, there is an upcoming awesome feature of partial rerun. Rerun can be isolated in a function.