JSFiddle - React, Tailwind, and code Playground

HTML

<div class="root-visual flex-container">
  <div class="lvl1-el1-visual"></div>
  <div class="lvl1-el2-visual flex-container non-scrollable">
    <div class="lvl2-el1-visual"></div>
    <div class="lvl2-el2-visual flex-container non-scrollable">
        <div class="lvl3-el1-visual"></div>
        <div class="lvl3-el2-visual scrollable">
          <span>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</span>
        </div>
        <div class="lvl3-el3-visual"></div>
    </div>
  </div>
</div>

CSS

/* IMPORTANT: what you need */

.flex-container {
  display: flex;
  flex-direction: column;
}

.flex-container > :not(.scrollable):not(.non-scrollable) {
  flex-shrink: 0;
}

.flex-container > .scrollable, .non-scrollable {
  flex-grow: 1;
}

.non-scrollable {
  overflow: hidden;
}

.scrollable {
  overflow: auto;
}

/* NOT IMPORTANT: visual styles and hard-coded sizes */

.root-visual {
  width: 300px;
  height: 300px;
  border: 1px solid blue;
}

.lvl1-el1-visual {
  height: 24px;
  background: orange;
}

.lvl1-el2-visual {
  border: 1px solid purple;
}

.lvl2-el1-visual {
  height: 24px;
  background: yellow;
}

.lvl2-el2-visual {
  border: 1px solid red;
}

.lvl3-el1-visual, .lvl3-el3-visual {
  height: 64px;
  background: green;
}

.lvl3-el2-visual {
  background: pink;
}