Самый простой способ. Шаблон forum > front > index
найти:
<li data-categoryID='{$category->_id}' class='cForumRow ipsBox ipsSpacer_bottom'>
<h2 class="ipsType_sectionTitle ipsType_reset cForumTitle">
<a href='#' class='ipsPos_right ipsJS_show ipsType_noUnderline cForumToggle' data-action='toggleCategory' data-ipsTooltip title='{lang="toggle_this_category"}'></a>
<a href='{$category->url()}'>{$category->_title}</a>
</h2>
{{if \IPS\forums\Forum::getMemberView() === 'grid'}}
<div class='ipsAreaBackground ipsPad' data-role="forums">
<div class='ipsGrid ipsGrid_collapsePhone' data-ipsGrid data-ipsGrid-minItemSize='250' data-ipsGrid-maxItemSize='500' data-ipsGrid-equalHeights='row'>
{{foreach $category->children() as $forum}}
{template="forumGridItem" group="index" app="forums" params="$forum"}
{{endforeach}}
</div>
</div>
{{else}}
<ol class="ipsDataList ipsDataList_large ipsDataList_zebra ipsAreaBackground_reset" data-role="forums">
{{foreach $category->children() as $forum}}
{template="forumRow" group="index" app="forums" params="$forum"}
{{endforeach}}
</ol>
{{endif}}
</li>
Заменить на:
{{if \IPS\Member::loggedIn()->language()->id == 1 AND $category->_id == 1}}
<li data-categoryID='{$category->_id}' class='cForumRow ipsBox ipsSpacer_bottom'>
<h2 class="ipsType_sectionTitle ipsType_reset cForumTitle">
<a href='#' class='ipsPos_right ipsJS_show ipsType_noUnderline cForumToggle' data-action='toggleCategory' data-ipsTooltip title='{lang="toggle_this_category"}'></a>
<a href='{$category->url()}'>{$category->_title}</a>
</h2>
{{if \IPS\forums\Forum::getMemberView() === 'grid'}}
<div class='ipsAreaBackground ipsPad' data-role="forums">
<div class='ipsGrid ipsGrid_collapsePhone' data-ipsGrid data-ipsGrid-minItemSize='250' data-ipsGrid-maxItemSize='500' data-ipsGrid-equalHeights='row'>
{{foreach $category->children() as $forum}}
{template="forumGridItem" group="index" app="forums" params="$forum"}
{{endforeach}}
</div>
</div>
{{else}}
<ol class="ipsDataList ipsDataList_large ipsDataList_zebra ipsAreaBackground_reset" data-role="forums">
{{foreach $category->children() as $forum}}
{template="forumRow" group="index" app="forums" params="$forum"}
{{endforeach}}
</ol>
{{endif}}
</li>
{{elseif \IPS\Member::loggedIn()->language()->id == 2 AND $category->_id == 4}}
<li data-categoryID='{$category->_id}' class='cForumRow ipsBox ipsSpacer_bottom'>
<h2 class="ipsType_sectionTitle ipsType_reset cForumTitle">
<a href='#' class='ipsPos_right ipsJS_show ipsType_noUnderline cForumToggle' data-action='toggleCategory' data-ipsTooltip title='{lang="toggle_this_category"}'></a>
<a href='{$category->url()}'>{$category->_title}</a>
</h2>
{{if \IPS\forums\Forum::getMemberView() === 'grid'}}
<div class='ipsAreaBackground ipsPad' data-role="forums">
<div class='ipsGrid ipsGrid_collapsePhone' data-ipsGrid data-ipsGrid-minItemSize='250' data-ipsGrid-maxItemSize='500' data-ipsGrid-equalHeights='row'>
{{foreach $category->children() as $forum}}
{template="forumGridItem" group="index" app="forums" params="$forum"}
{{endforeach}}
</div>
</div>
{{else}}
<ol class="ipsDataList ipsDataList_large ipsDataList_zebra ipsAreaBackground_reset" data-role="forums">
{{foreach $category->children() as $forum}}
{template="forumRow" group="index" app="forums" params="$forum"}
{{endforeach}}
</ol>
{{endif}}
</li>
{{endif}}
Соответственно \IPS\Member::loggedIn()->language()->id и $category_id указать свои.