Like this
var $filterListMenu = $('ul.category-menu');
var filterListMenuSize = $filterListMenu.length;
$filterListMenu.each((i, el) => {
let count = $(el).children('li').length;
$(el).next('button').toggleClass('d-none', count <= 6);
});
.d-none {
display: none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<div class="sidebar">
<ul class="category-menu" id="category1">
<li>First Ul li1 </li>
<li>First Ul li2 </li>
<li>First Ul li3 </li>
<li>First Ul li4</li>
</ul>
<button class="btn" data-toggle="collapse" href="#category1" role="button" aria-expanded="false" aria-controls="category1">Click Here</button>
<ul class="category-menu" id="category2">
<li>Second Ul li1 </li>
<li>Second Ul li2 </li>
<li>Second Ul li3 </li>
<li>Second Ul li4</li>
<li>Second Ul li5</li>
<li>Second Ul li6</li>
<li>Second Ul li7</li>
</ul>
<button class="btn" data-toggle="collapse" href="#category2" role="button" aria-expanded="false" aria-controls="category2">Click Here</button>
</div>
or
var $buttons = $('.sidebar .btn').each(function() {
$(this).toggleClass('d-none',
$(this).prev('.category-menu').find('li').length <= 6)
})
.d-none {
display: none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<div class="sidebar">
<ul class="category-menu" id="category1">
<li>First Ul li1 </li>
<li>First Ul li2 </li>
<li>First Ul li3 </li>
<li>First Ul li4</li>
</ul>
<button class="btn" data-toggle="collapse" href="#category1" role="button" aria-expanded="false" aria-controls="category1">Click Here</button>
<ul class="category-menu" id="category2">
<li>Second Ul li1 </li>
<li>Second Ul li2 </li>
<li>Second Ul li3 </li>
<li>Second Ul li4</li>
<li>Second Ul li5</li>
<li>Second Ul li6</li>
<li>Second Ul li7</li>
</ul>
<button class="btn" data-toggle="collapse" href="#category2" role="button" aria-expanded="false" aria-controls="category2">Click Here</button>
</div>