Hide/show Children on checkbox backend admin

I am trying to Hide/show large Children based on checkbox option backend admin through css.I tried following

ul.categorychecklist input[type=”checkbox”]:checked +label + .selectit {
    display: block!important;
}

ul.categorychecklist ul {
    margin-top: 15px;
    display: none;
}
<label class="selectit"><input value="464" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-464"> AUDI</label>
<ul class="children">

<li id="brand_year_model-500" class="popular-category"><label class="selectit"><input value="500" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-500"> A3</label> <ul class="children">

<li id="brand_year_model-1909"><label class="selectit"><input value="1909" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-1909"> 2019</label></li>

<li id="brand_year_model-1075" class="popular-category"><label class="selectit"><input value="1075" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-1075"> 2020</label></li>

<li id="brand_year_model-1352" class="popular-category"><label class="selectit"><input value="1352" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-1352"> 2021</label></li>

<li id="brand_year_model-1629"><label class="selectit"><input value="1629" type="checkbox" name="tax_input[brand_year_model][]" id="in-brand_year_model-1629"> 2022</label></li>
    </ul>
</li>



    </ul>
</li>
</ul>

But i am unable to do so in backend.With a long list it looks untidy.Kindly see.Looking for show category children s only when checked