JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en-us"><head>
<meta charset="utf-8">

<style>
 * { min-height: 0 }
.topicEditHeader, ul.nav-tabs > li, .shortenText {
  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;
}

html, body{
  margin: 0;
}

html, body {
  height: 100vh;
  max-height: 100vh;
  /*height: 100vw;*/
  /*overflow: hidden;*/
}

/** .page **/
.page {
  display: flex;
  flex-direction: column;

  position:absolute;
  width: 100vw;
  height: 100vh;
  max-height: 100vh;
}

.page > menu {
  flex-grow: 0;
  flex-shrink: 0;
}
.page > #divBelowStatusbar {
  flex-grow: 1;
  flex-shrink: 1;
}
/** END .page **/

/** menu **/
menu {
  background-color: gray;
  margin-top: 0;
  margin-bottom: 3px;
  /*position: absolute;*/
  /*top: 0px;*/
}

menu > li > a {
  color: white;
}

menu > li {
  padding-right: 20px;
  display: inline-flex;
  list-style-type: none;
}
/** END menu **/

/** #divBelowStatusbar **/
#divBelowStatusbar {
  flex-direction: column;
  display: flex;
}

#divBelowStatusbar > #errors {
  flex-grow: 0;
}

#divBelowStatusbar > #contentArea {
  /*flex: 1;*/
  flex-shrink: 1;
  flex-grow: 1;
}
/** END #divBelowStatusbar **/


/** #contentArea **/
#divBelowStatusbar > #contentArea {
  margin-right: 20px;
  display: flex;
  flex: 1;
}
/** END #contentArea **/


/** .tabContent **/
.tabContent {
  display: flex;
  flex-direction: column;

  flex-grow: 1;
}

.tabContent > .paneHeader {
  display: flex;

  flex-shrink: 0;
  flex-grow: 0;

  padding-bottom: 10px;
}

.tabContent > .paneHeader > .paneHeaderHeading {
  flex-grow: 1;
}

.tabContent > .paneHeader > .paneHeaderTools {
  flex-shrink: 0;
  flex-grow: 0;
}

.tabContent > .content {
  overflow-y: scroll;

  flex-grow: 1;
  min-height: 300px;
}

/** TODO: nest **/
.cmbtab {
  flex-grow: 1; flex-shrink: 1;
}

.tabHeadersContainer {
  display: flex;

  flex-shrink: 0;
}

.tabContentsContainer {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
}

.tabContentsContainer > div {
  display:...