Callouts, code, tasks and more

Beyond paragraphs and lists, a few blocks do a lot of the work in team documents: callouts flag what matters, code blocks keep code readable, task lists track what’s left, footnotes keep asides out of the way, and collapsible sections tuck away detail until someone wants it.

Add a callout

A callout is a highlighted note, for a tip or a warning a reader shouldn’t miss. Choose Callout in the slash menu, or type:

> [!NOTE]
> Text of the note.

The types are NOTE, TIP, IMPORTANT, WARNING and CAUTION, and the > [!TYPE] line has to be on its own. These are the same callouts GitHub shows, so they look right there too.

Add a code block

Choose Code block in the slash menu, or type three backticks. A list suggests common languages (bash, css, go, javascript, json, python, sql, typescript, yaml and more), and many others are highlighted too.

```python
print("hello")
```

In Live view and the Split preview, each code block has a Copy button that copies just the code, without the backticks. To change how code is colored, open Editor settings and choose Code colors: Default, Soft or High contrast. If you use a Color vision mode, Default and Soft switch to colors that stay apart for that color blindness.

Number the lines of a code block

Add = after the language to number the lines, or = and a number to start somewhere else, which helps when you quote part of a longer file:

```js=101
const total = items.reduce((sum, item) => sum + item.price, 0)
```

js= starts at 1 and js=101 at 101. The form js {startline=101} works too. The numbers sit in a narrow column beside the code. They aren’t part of the text: Copy and selecting the code copy only the code, and screen readers skip the numbers.

Source view shows the line as you typed it. Download .md for other tools writes plain js, because other tools would read js=101 as the language name.

Make a task list

Type - [ ] , or use Task list in the toolbar or the slash menu. To tick a task, click its box in Live view, or put the cursor on the line and press Ctrl+Enter (Cmd+Enter). A ticked task is written - [x].

Assign a task

Mention a person in a task to assign it to them, and add a date to set its due date. Type @ and choose the person from the list; a name typed without choosing it stays plain text. In Live view it reads like this:

- [ ] Review the brief @Ada 2026-11-20

If they can open the document, they get one notification, and the open task appears in their My tasks in the sidebar, ordered by due date. Tick the box to complete it.

Add a footnote

Write [^1] where the note belongs, and the note itself on its own line:

Markdown is portable.[^1]

[^1]: Any markdown editor can open it.

In Live view the reference shows as a small number. Ctrl+click (Cmd+click) it to jump to the note.

Add a collapsible section

A collapsible section shows a one-line summary, and the reader opens it to see the rest. It’s useful for long logs and optional detail. Choose Collapsible section in the slash menu, or type:

<details>
<summary>Full test output</summary>

Any markdown goes here: lists, code, tables, even another collapsible section.

</details>

Write <details open> instead to have the section start open.

Colletta recognizes these exact lines only, the way GitHub writes them: <details> or <details open> on a line, then <summary>...</summary> on the next, a blank line, the content, and </details> on its own line. Other HTML is still never drawn as HTML.

• In the Split preview, the section is open or closed as written, and you click the summary to open or close it.
• In Live view, every section shows its content while you edit, with a line down the left side. Click the triangle beside the summary to fold one away. Folding only changes your screen: the document and everyone else’s view stay as they are. A folded section opens again when your cursor moves into it.

In Live view, sections are drawn only at the top level of the document. Inside a list or a quote they show as typed, though the preview still draws them.