Hello, please tell me how I can display a custom field in the search at the top, which is in the inc.search.php file where the search is by name, category and city, I need to add a custom field by which I want the search to work as well. Is it possible to do this and how? Thanks for the answers.

You must move hook functions.

  if(osc_search_category_id()) {
    osc_run_hook('search_form', osc_search_category_id());
  } else {
    osc_run_hook('search_form');
  }

Tell me in which file I need to add this hook code?

You must move hook functions.

  if(osc_search_category_id()) {
    osc_run_hook('search_form', osc_search_category_id());
  } else {
    osc_run_hook('search_form');
  }

Its code in search.php that is already there and display plugin data.