I have a need to be able to customize which categories are displayed through the portfolio template. Hopefully something i can add manually to one of these tags? I have duplicated the Portfolio template so I can adjust it for a few different pages and create multiple templates.

This is for a furniture company with categories as follows:

Style category name parent (Milan) > Type of Furniture category (Chair) > Chair Product (product page ie portfolio page using the tags "Milan, Chair")

<!-- Portfolio Filters --> 
                        <ul id="filters" class="<?php echo sanitize_html_class( $soho_filters_class ); ?>">
                            <li class="filter-line"></li>
                            <li><a id="all" href="#" data-filter="*" class="active"><?php esc_html_e('All', 'soho'); ?></a></li>    
                            <?php
                            $soho_portfolio_category = get_terms('portfolio_category', array( 'hide_empty' => 0 ));

                            if($soho_portfolio_category){

                                foreach($soho_portfolio_category as $portfolio_cat){
                            ?>
                            <li><a href="#" data-filter=".<?php echo sanitize_title( $portfolio_cat->slug ); ?>"><?php echo wp_kses_post( $portfolio_cat->name ); ?></a></li>
                            <?php
                                }
                            }
                            ?>
                        </ul>
                        <!--/Portfolio Filters -->
                        <!-- Portfolio -->
                        <div id="portfolio-wrap" class="<?php echo esc_attr( $soho_margins ); ?>">
                            <div id="portfolio" <?php if( $soho_use_lightbox ){ echo 'class="mfp-gallery"'; } ?> data-col="<?php echo esc_attr( $soho_columns ); ?>">
                            <?php
                            
                                $soho_paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
                                $soho_args = array(
                                            'post_type' => 'soho_portfolio',
                                            'paged' => $soho_paged,
                                            'posts_per_page' => $soho_max_items,
                                         );
                            
                                $soho_portfolio = new WP_Query( $soho_args );

                                while( $soho_portfolio->have_posts() ){
                                
                                    $soho_portfolio->the_post();
                                
                                    if( $soho_use_lightbox ){
                                        
                                        get_template_part('sections/portfolio_section_lightbox_item');
                                    }
                                    else {
                                    
                                        get_template_part('sections/portfolio_section_item');
                                    }
                                    
                                }
                            
                                wp_reset_postdata();
                            
                            ?>
                            </div>
                        </div>
                        <!--/Portfolio -->

Ok sounds good... but i cannot get it to work... am I missing something?

<li><a id="all" href="#" data-filter="*" class="active"><?php esc_html_e('All', 'soho'); ?></a></li>    
                            <!-- CUSTOM Filters --> 
                            <li><a id="#" href=".milan" data-filter="milan"><?php esc_html_e('Milan', 'soho'); ?></a></li>    
                        </ul>
                        <!--/Portfolio Filters -->
                        <!-- Portfolio -->
                        <div id="portfolio-wrap" class="<?php echo esc_attr( $soho_margins ); ?>">
                            <div id="portfolio" <?php if( $soho_use_lightbox ){ echo 'class="mfp-gallery"'; } ?> data-col="<?php echo esc_attr( $soho_columns ); ?>">
                            <?php
                            
                                $soho_paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
                                $soho_args = array(
                                            'post_type' => 'soho_portfolio',
                                            'paged' => $soho_paged,
                                            'posts_per_page' => $soho_max_items,
                                            'tax_query' => array(
                                                                    'relation' => 'AND',
                                                                    array(
                                                                        'taxonomy' => 'category',
                                                                        'field'    => 'slug',
                                                                        'terms'    => array( 'milan', 'milan-chairs',  ),
                                                                    ),
    
                                                                ),
                                         );
                            
                                $soho_portfolio = new WP_Query( $soho_args );

                                while( $soho_portfolio->have_posts() ){
                                
                                    $soho_portfolio->the_post();
                                
                                    if( $soho_use_lightbox ){
                                        
                                        get_template_part('sections/portfolio_section_lightbox_item');
                                    }
                                    else {
                                    
                                        get_template_part('sections/portfolio_section_item');
                                    }
                                    
                                }
                            
                                wp_reset_postdata();
                            
                            ?>

So I finally got this to work... I needed to have the right taxonomy.

portfolio_category

<?php
                                $soho_paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
                                $soho_args = array(
                                            'post_type' => 'soho_portfolio',
                                            'paged' => $soho_paged,
                                            'posts_per_page' => $soho_max_items,
                                            //Custom category displayed
                                            'tax_query' => array( 
                                                    array(
                                                      'taxonomy' => 'portfolio_category',
                                                       'field'    => 'slug',
                                                       'terms'    => array( 'patriarch_milan'),
                                                       ),
                                                                            
                                                                        ),
                                                                                                             );
                                $soho_portfolio = new WP_Query( $soho_args );

                                while( $soho_portfolio->have_posts() ){
                                
                                    $soho_portfolio->the_post();
                                
                                    if( $soho_use_lightbox ){
                                        
                                        get_template_part('sections/portfolio_section_lightbox_item');
                                    }
                                    else {
                                    
                                        get_template_part('sections/portfolio_section_item');
                                    }
                                    
                                }
                            
                                wp_reset_postdata();
                            
                            ?>