add troubleshooting entry

Author: chargome

docs/platforms/javascript/common/troubleshooting/index.mdx

@@ -540,4 +540,10 @@ Learn more about fixing these caching issues in the <PlatformLink to="/sourcemap
   </Expandable>
 </PlatformSection>
 
+<PlatformSection supported={['javascript.nextjs']}>
+  <Expandable permalink title="Using the Sentry Next SDK in a Nx monorepo">
+    If you want to set up Sentry's Next.js SDK in an Nx monorepo context, please refer to [this guide](https://nx.dev/recipes/next/next-config-setup#manually-composing-plugins-nx-15-and-prior).
+  </Expandable>
+</PlatformSection>
+
 If you need additional help, you can [ask on GitHub](https://github.com/getsentry/sentry-javascript/issues/new/choose). Customers on a paid plan may also contact support.