st.form is a very good component, it provides us an area to fill with st.text_input or st.selectbox etc.
in some cases, if we put a lot of content between st.form and st.form_submit_button, we want to make space layout become more concise and crisp by folding the content between st.form and st.form_submit_button after button be clicked.
hope this will become a new function inside the st.form in the near future.
my advice, add an argument like this:
st.form_submit_button("click me to submit", fold_after_click=True)