Type @<username> in the post and it should auto highlight.

Do you mean add a Today Widget on iOS?

https://developer.apple.com/design/human-interface-guidelines/ios/extensions/widgets/

If so, what would you like to see?

Coming in v5.0

The Browser account already does this for you.

Just replace image urls with custom urls.

The image for the user. Import an image via your library.

Enable 'Follows User' for the selected user

Already in the app. Tap on an existing username.

Once I've finished working on the fake DMs