Create a note mentioning a selected member. This operation is experimental.
Requires `notes:write`; finding the recipient first requires `notes:read`.

Use [Selectable Team Members](https://developers.buffer.com/examples/selectable-team-members.md) to select a recipient from the Post's channel. Replace the example `serviceEntityId` with the selected member's complete `urn`. See [Notes](https://developers.buffer.com/guides/notes.md#add-a-mention) for the full workflow.

```graphql
mutation CreateNoteWithMention {
  createCollaborationNote(input: {
    subject: { postId: "YOUR_POST_ID" }
    text: "@Alex please review the revised caption."
    annotations: [{
      type: mention
      serviceEntityId: "SELECTED_MEMBER_URN"
      content: "@Alex"
      text: "@Alex"
      indices: [0, 5]
    }]
  }) {
    __typename
    ... on CreateCollaborationNoteSuccess {
      edge {
        node {
          id
          text
          annotations { type serviceEntityId content text indices }
          allowedActions
        }
      }
    }
    ... on MutationError { message }
  }
}
```

For a channel-less draft, find recipients with organization scope and use `{ contentItemId: "YOUR_CONTENT_ITEM_ID" }` as the subject. Update the annotation span when changing the text. Buffer rejects the entire write if any recipient cannot read the subject's Notes.