JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mobile-tools">
<input type="button" id="navigation-button" value="FooBar">
<div id="search-box"><input type="search"></div>
</div>

CSS

#mobile-tools {
    display: flex;
}
#navigation-button {
    flex: 0 auto;
}
#search-box {
    flex: 1;
}
#search-box input[type="search"] {
  width: 100%;
}