Example:
<div class="pageProduct">
<div class="pageProduct__section pageProduct__secondChildClass"></div>
<div class="pageProduct__section></div>
<div class="pageProduct__section></div>
<div class="pageProduct__section></div>
</div>
I don't want to use a modifier and I'm not sure if this syntax is okay.
Sure, it's called mix. There also can be a mix of a block and an element on the same DOM node.