Вы можете установить отрицательное поле и добавить отступ сверху
.orange{
background: orange;
margin-top: -40px;
padding-top: 50px;
}
.pink{
background: pink;
margin-top: -40px;
padding-top: 50px;
}
.title{
z-index: 1;
background: red; //I add red to test
}
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
<div class="container-fluid d-flex flex-column vh-100 overflow-hidden">
<nav class="navbar navbar-light bg-light navbar-expand px-0 flex-shrink-0">
<a class="navbar-brand" href="#">App</a>
<ul class="navbar-nav">
<li class="nav-item"><a href="#" class="nav-link">Home</a></li>
<li class="nav-item"><a href="#" class="nav-link">Link</a></li>
<li class="nav-item"><a href="#" class="nav-link">Link</a></li>
<li class="nav-item"><a href="#" class="nav-link">More</a></li>
</ul>
<ul class="navbar-nav ml-auto">
<li class="nav-item"><a href="#" class="nav-link">Options</a></li>
</ul>
</nav>
<div class="row flex-grow-1 overflow-hidden">
<div class="col-2 mh-100 overflow-auto py-2">
<h6>Sidebar</h6>
<ul class="nav flex-column bg-info rounded">
<li class="nav-item">
<a class="nav-link text-white" href="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link text-white" href="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link text-white" href="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link text-white" href="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link text-white" href="#">Link</a>
</li>
</ul>
</div>
<div class='col mh-100 overflow-auto'>
<div class='row flex-grow-1'>
<div class='col mh-100 overflow-auto'>
<div class='row flex-shrink-0'>
<div class="col title">
<h3>Body content</h3>
</div>
</div>
<div class='row flex-grow-1'>
<div class="col pink mh-100 overflow-auto">
<h2>This div must fill remaining height</h2>
<p>Ethical Kickstarter PBR asymmetrical lo-fi. Dreamcatcher street art Carles, stumptown gluten-free Kickstarter artisan Wes Anderson wolf pug. Godard sustainable you probably haven't heard of them, vegan farm-to-table Williamsburg slow-carb readymade disrupt deep v. Meggings seitan Wes Anderson semiotics, cliche American Apparel whatever. Helvetica cray plaid, vegan brunch Banksy leggings +1 direct trade. Wayfarers codeply PBR selfies. Banh mi McSweeney's Shoreditch selfies, forage fingerstache food truck occupy YOLO Pitchfork fixie iPhone fanny pack art party Portland.</p>
</div>
</div>
</div>
<div class='col mh-100 overflow-auto'>
<div class='row flex-shrink-0'>
<div class="col title">
<h3>Body content</h3>
</div>
</div>
<div class='row flex-grow-1'>
<div class="col orange mh-100 overflow-auto">
<h2>This div must fill remaining height</h2>
<p>Ethical Kickstarter PBR asymmetrical lo-fi. Dreamcatcher street art Carles, stumptown gluten-free Kickstarter artisan Wes Anderson wolf pug. Godard sustainable you probably haven't heard of them, vegan farm-to-table Williamsburg slow-carb readymade disrupt deep v. Meggings seitan Wes Anderson semiotics, cliche American Apparel whatever. Helvetica cray plaid, vegan brunch Banksy leggings +1 direct trade. Wayfarers codeply PBR selfies. Banh mi McSweeney's Shoreditch selfies, forage fingerstache food truck occupy YOLO Pitchfork fixie iPhone fanny pack art party Portland.</p>
</div>
</div>
</div>
</div>
</div>
</div>
</div>