what2watch/templates/elements/add_watch_button.html

<form id="add-watch-{{self.watch}}">
    <button hx-post="/add/watch" hx-target="#add-watch-{{watch}}" hx-trigger="click" hx-swap="outerHTML">add</button>
    <select name="public" id="add-public-watch">
        <option value="true">public</option>
        <option value="false">private</option>
    </select>
    <input type="hidden" name="watch" value="{{self.watch}}">
</form>