Sidebar link / top button to PM admin

[Moin]

If you want to add the link somewhere else, there are also Customization > Theme component to do that. For example
Custom Header Links
Custom Top Navigation Links

@rahim123

But ideally I"d like to pre-fill the recipient too

Creating pre-filled personal message links

This guide describes how to create a link to start a new personal message with pre-filled information, including best practices. Required user level: All users Discourse allows you to compose a new personal message with pre-filled information via URL parameters. This can save time and ensure consistency for common messages. Structure of the URL To create a new pre-filled message, format your URL like this: https://discourse.example.com/new-message?username…