By default, the platform does not have this option. You can use the following CSS code.

Please follow the steps below:

    1. Go to BuddyBoss - Theme Options

    2. Under Custom Codes, enable CSS

    3. Append the following:

@media (max-width: 767px) {
  .btn-new-topic {
    display: none;
  }
}

Note: Any modifications are considered as custom work already. Know more about our Support policy here: https://www.buddyboss.com/support-policy/

Screenshots

Without Code:

With Code: