# Expert

> How to edit an app’s YAML directly in the Expert tab, what a validation error looks like, and which settings can only be changed here.

Canonical HTML page: https://conclude.io/doc/apps/editor/expert/
Last updated: 2026-11-02

---

A builder never needs this tab. The other tabs write to the same YAML. Open this tab when a setting has no visual control, or to paste in YAML you wrote elsewhere.

![The Expert tab showing an app's YAML in the code editor](https://conclude.io/images/doc/dev-app-settings-expert.webp)

## The YAML editor

The tab is a single code editor that holds the complete app YAML. It has YAML syntax highlighting and line numbers. There is no export control. To take a copy, select the text and copy it. Save with **Save** or Ctrl+S (Cmd+S on macOS).

Two aids are built in.

- In role and alert fields such as `members`, `admins`, `superusers`, `alert` and `to`, typing `@` lists users and user groups. Typing `#` lists channels. The `owner` field lists users only
- The editor quotes values in those fields for you, and any value that starts with `@`. The quotes stop YAML from misreading them

As soon as the document parses, the other tabs show what you typed. Editing a visual tab regenerates the YAML shown here.

## Validation and errors

The editor validates the document on every change, before anything reaches the server. It reports these errors:

- a YAML syntax error
- a missing `name`, `label` or `attributes` section
- a missing `title` attribute
- a duplicate attribute name
- an attribute without a `label`, or with an unknown `type`
- a malformed role or `mode` value

An error appears as a marker in the line gutter next to the offending line. Hover over the marker to read the message. A message reads like `There is an error in the document at line 12, column 3` or `Missing mandatory attribute *title*`.

While the document has an error, **Save** is disabled and Ctrl+S does nothing. The server checks the app again on save. See [Validation rules](https://conclude.io/doc/reference/yaml/#validation-rules).

## Comments and formatting

Comments, blank lines and key order between top-level sections survive a save from any tab. Comments and blank lines inside a section are dropped, for example between attributes. Editing a visual tab regenerates the YAML shown here without comments. On save, the server merges the new state into the last saved document.

## When you need this tab

Some sections have no visual control. You can only edit them here.

- `triggers` and `scripts`. The one exception is a trigger's `agent` and `mode` fields, which the Agents tab sets. See [Triggers](https://conclude.io/doc/reference/triggers/) and [Scripting](https://conclude.io/doc/reference/scripting/). Scripts run only when scripting is [switched on for the organization](https://conclude.io/doc/reference/scripting/#enabling-scripting)
- `lookup`, the lookup endpoint. See [Lookup endpoints](https://conclude.io/doc/apps/integrations/lookup/)
- `review`, the review step. See [Review](https://conclude.io/doc/reference/yaml/#review)
- `admins` and `superusers` under `roles`. The [Roles](https://conclude.io/doc/apps/editor/roles/) tab does not expose them. See [Macros and roles](https://conclude.io/doc/reference/macros-and-roles/#roles-block)

The [YAML reference](https://conclude.io/doc/reference/yaml/) has every key. For the other tabs, see [the editor](https://conclude.io/doc/apps/editor/).