/wp-content/plugins/kboard/skin/play-video/list.php 파일입니다.

아마 아래와 같은 코드를 찾으실 수 있을 겁니다.

<?php if($board->use_category):?>
    <?php if($board->initCategory1()):?>
    <div class="kboard-attr-row">
        <label class="attr-name" for="kboard-select-category1"><?php echo __('Category', 'kboard')?>1</label>
        <div class="attr-value">
            <select id="kboard-select-category1" name="category1">
                <option value=""><?php echo __('Category', 'kboard')?> <?php echo __('Select', 'kboard')?></option>
                <?php while($board->hasNextCategory()):?>
                <option value="<?php echo $board->currentCategory()?>"<?php if($content->category1 == $board->currentCategory()):?> selected="selected"<?php endif?>><?php echo $board->currentCategory()?></option>
                <?php endwhile?>
            </select>
        </div>
    </div>
    <?php endif?>
    
    <?php if($board->initCategory2()):?>
    <div class="kboard-attr-row">
        <label class="attr-name" for="kboard-select-category2"><?php echo __('Category', 'kboard')?>2</label>
        <div class="attr-value">
            <select id="kboard-select-category2" name="category2">
                <option value=""><?php echo __('Category', 'kboard')?> <?php echo __('Select', 'kboard')?></option>
                <?php while($board->hasNextCategory()):?>
                <option value="<?php echo $board->currentCategory()?>"<?php if($content->category2 == $board->currentCategory()):?> selected="selected"<?php endif?>><?php echo $board->currentCategory()?></option>
                <?php endwhile?>
            </select>
        </div>
    </div>
    <?php endif?>
<?php endif?>

위의 코드 대신 아래의 코드를 추가해서 테스트 해보시겠어요? (5.3버전의 default 스킨에 있는 코드 입니다.)

<?php if($board->use_category == 'yes'):?>
<div class="kboard-category category-pc">
    <?php if($board->initCategory1()):?>
        <ul class="kboard-category-list">
            <li<?php if(!kboard_category1()):?> class="kboard-category-selected"<?php endif?>><a href="<?php echo $url->set('category1', '')->set('pageid', '1')->set('target', '')->set('keyword', '')->set('mod', 'list')->tostring()?>"><?php echo __('All', 'kboard')?></a></li>
            <?php while($board->hasNextCategory()):?>
            <li<?php if(kboard_category1() == $board->currentCategory()):?> class="kboard-category-selected"<?php endif?>>
                <a href="<?php echo $url->set('category1', $board->currentCategory())->set('pageid', '1')->set('target', '')->set('keyword', '')->set('mod', 'list')->toString()?>"><?php echo $board->currentCategory()?></a>
            </li>
            <?php endwhile?>
        </ul>
    <?php endif?>
    
    <?php if($board->initCategory2()):?>
        <ul class="kboard-category-list">
            <li<?php if(!kboard_category2()):?> class="kboard-category-selected"<?php endif?>><a href="<?php echo $url->set('category2', '')->set('pageid', '1')->set('target', '')->set('keyword', '')->set('mod', 'list')->tostring()?>"><?php echo __('All', 'kboard')?></a></li>
            <?php while($board->hasNextCategory()):?>
            <li<?php if(kboard_category2() == $board->currentCategory()):?> class="kboard-category-selected"<?php endif?>>
                <a href="<?php echo $url->set('category2', $board->currentCategory())->set('pageid', '1')->set('target', '')->set('keyword', '')->set('mod', 'list')->toString()?>"><?php echo $board->currentCategory()?></a>
            </li>
            <?php endwhile?>
        </ul>
    <?php endif?>
</div>
<?php endif?>

css 속성등은 집접 확인해서 추가하셔야 합니다.