title: How to fix 'The feature "multi platform projects" is experimental and should be enabled explicitly' warning in IntelliJ IDEA
body: <p>Whenever I write an <code>expect</code> function in IntelliJ IDEA, I get the following warning:<br />
  <code>The feature &quot;multi platform projects&quot; is experimental and should be enabled explicitly</code></p>
  <p>Where can enable this feature? I already searched the settings and didn't find a way to disable that warning.</p>
  <p>Compilation with gradle works fine.</p>