How can I hide the add button from sidebar

To only hide it for regular users, you can make a slight adjustment to the above CSS:

body:not(.staff) {
  [data-section-name="community"] {
    .sidebar-section-header-button {
      display: none;

so now it will only apply to users that are not staff

We have a tutorial about how to make these kind of CSS changes here: Make CSS changes on Your Site

are people expecting it to add a sidebar item rather than create a new topic? or something else?