When you’re registering new post type with register_post_type, you can pass labels parameter (which is an array of labels used for that CPT).
You can customize these labels:
- ‘name’ – general name for the post type, usually plural. The same and overridden by $post_type_object->label. Default is Posts/Pages
- ‘singular_name’ – name for one object of this post type. Default is Post/Page
- ‘add_new’ – the add new text. The default is “Add New” for both hierarchical and non-hierarchical post types. When internationalizing this string, please use a gettext context matching your post type. Example: _x(‘Add New’, ‘product’);
- ‘add_new_item’ – Default is Add New Post/Add New Page.
- ‘edit_item’ – Default is Edit Post/Edit Page.
- ‘new_item’ – Default is New Post/New Page.
- ‘view_item’ – Default is View Post/View Page.
- ‘view_items’ – Label for viewing post type archives. Default is ‘View Posts”https://wordpress.stackexchange.com/”View Pages’.
- ‘search_items’ – Default is Search Posts/Search Pages.
- ‘not_found’ – Default is No posts found/No pages found.
- ‘not_found_in_trash’ – Default is No posts found in Trash/No pages found in Trash.
- ‘parent_item_colon’ – This string isn’t used on non-hierarchical types. In hierarchical ones the default is ‘Parent Page:’.
- ‘all_items’ – String for the submenu. Default is All Posts/All Pages.
- ‘archives’ – String for use with archives in nav menus. Default is Post Archives/Page Archives.
- ‘attributes’ – Label for the attributes meta box. Default is ‘Post Attributes”https://wordpress.stackexchange.com/”Page Attributes’.
- ‘insert_into_item’ – String for the media frame button. Default is Insert into post/Insert into page.
- ‘uploaded_to_this_item’ – String for the media frame filter. Default is Uploaded to this post/Uploaded to this page.
- ‘featured_image’ – Default is Featured Image.
- ‘set_featured_image’ – Default is Set featured image.
- ‘remove_featured_image’ – Default is Remove featured image.
- ‘use_featured_image’ – Default is Use as featured image.
- ‘menu_name’ – Default is the same as
name. - ‘filter_items_list’ – String for the table views hidden heading.
- ‘items_list_navigation’ – String for the table pagination hidden heading.
- ‘items_list’ – String for the table hidden heading.
- ‘name_admin_bar’ – String for use in New in Admin menu bar. Default is the same as
singular_name.
As you can see, add_new_item is the label that should solve your problem.