Redwoodcity

WP Notepad puts a notepad textarea on your site. Visitors can jot notes without logging in, and notes are kept in their own browser’s LocalStorage — by default nothing is sent to or stored on the server.
Add a notepad in three ways:
<ul>
<li>Classic widget — add the “Notepad” widget to any widget area.</li>
<li>Block — insert the “WP Notepad” block in the editor.</li>
<li>Shortcode — place <code>[wpnotepad]</code> in post content or theme templates.</li>
</ul>
Features:
<ul>
<li>Notes auto-save to the browser as you type, and are restored on return.</li>
<li>Live character counter and a confirm-protected Clear button.</li>
<li>The textarea grows automatically to fit its content.</li>
<li>Copy to clipboard, download as a .txt file, or import a note from a file.</li>
<li>Multiple notes in one notepad via tabs.</li>
<li>Optional auto-delete (TTL): notes expire after a configurable number of days.</li>
<li>Optional, opt-in cross-device sync for logged-in users (see below). Disabled by default.</li>
<li>Accessibility: labelled textarea, character-count association, polite save announcements and visible focus styles.</li>
<li>Block styling via the editor’s color, typography, spacing and alignment controls.</li>
<li>Available in English and Japanese.</li>
</ul>
Privacy / cross-device sync: By default notes live only in the visitor’s browser and are never stored on the server. An administrator may optionally enable “cross-device sync” under Settings → WP Notepad. When enabled, only logged-in users’ notes are saved to their own WordPress user account (user meta) and synced across their devices via the REST API. Guests (logged-out visitors) always remain LocalStorage-only.

WP Notepad

Add a notepad via a widget, block or shortcode. Notes save to the browser (LocalStorage) — no login required — with optional opt-in cross-device sync.

Iftekhar Bhuiyan

AdminPad allows WP site admin (only) to write down simple note from WP dashboard using simple widget. Deleting this plugin will also delete data saved by this plugin on your database.
Features: 
* Light weight plugin. 
* Simple user interface.

AdminPad

AdminPad is a simple note taker for site administrator only.

WP Notepad vs AdminPad