chore: link to the config to flatten custom claims in Hydra

docs/hydra/guides/oauth2-webhooks.mdx

@@ -210,6 +210,13 @@ You cannot override the token subject.
 
 :::
 
+### Add custom claims to top level
+
+By default, all custom claims are mirrored under the `ext` claim in the token.
+
+To flatten custom claims directly into the top level token instead of nesting them under `ext`, use the following
+[configuration](../../oauth2-oidc/jwt-access-token#adding-custom-claims-to-top-level).
+
 ### Refresh token
 
 If a webhook for `refresh_token` grant type fails with a non-graceful result, the refresh flow will fail and the supplied

docs/oauth2-oidc/jwt-access-token.mdx

@@ -156,6 +156,8 @@ Which results in the following access token:
 }
 ```
 
+### Add custom claims to top level
+
 If you want `some_custom_claim` to be added to the top level (instead of a nested level) in the access token, you need to modify
 the `/oauth2/allowed_top_level_claims` configuration: