Reset multiselect to default values using a checkbox

[xinnyuann]

I did the same thing with several st.sidebar.multiselect, guess you can try this out by using session state: an example here is Reseting the app via a button (if you are using latest versio of streamlit, please use this gist: https://gist.github.com/tvst/036da038ab3e999a64497f42de966a92)