KODE UNTUK KESELURUHAN JUDUL PADA HOME, KATEGORI, TAG
====================================================
function titleLimitChar($title){
        if(strlen($title) > 30 && !(is_single()) && !(is_page())){ // not in single post page and page.
            $title = substr($title,0,30) . "..";
        }
        return $title;
    }
    add_filter( 'the_title', 'titleLimitChar' );

KODE HANYA UNTUK KATEGORI TERTENTU (SATU, DUA, ATAU LEBIH KATEGORI)
============================
function titleLimitChar($title){
        if(is_category( '9' )){
            if(strlen($title) > 30 && !(is_single()) && !(is_page())){ // not in single post page and page.
                $title = substr($title,0,30) . "..";
            }
             return $title;
        }else{
         return $title;
        }   


    }
    add_filter( 'the_title', 'titleLimitChar' );

PENJELASAN:

in the is_category() you use category id, category name and catgory-slug etc.

For Multiple categories just pass array in the parameter as

array( 9, 'blue-cheese', 'Stinky Cheeses' )
Other uses to check specific category or categories as below from the WordPress developer portal.

is_category();
// When any Category archive page is being displayed.

is_category( '9' );
// When the archive page for Category 9 is being displayed.

is_category( 'Stinky Cheeses' );
// When the archive page for the Category with Name "Stinky Cheeses" is being displayed.

is_category( 'blue-cheese' );
// When the archive page for the Category with Category Slug "blue-cheese" is being displayed.

is_category( array( 9, 'blue-cheese', 'Stinky Cheeses' ) );

SUMBER: https://stackoverflow.com/questions/45649231/how-to-limit-the-title-of-wordpress-to-specific-categories