The “Clear Cache” or “C” button feature was removed around version 0.89 and is only available to developers now. I have only used streamlit 0.88 since then because clearing cache is essential to the user experience. Basically, the applet is querying Git branches on a repo with thousands of branches so that would be best done cached, but cache clearing is necessary when a new branch is added to git.
Ideally, there would just be an option in the page_setup function or whatever.