The plugin adds several variables that can be used in QGIS expressions:

Variable name Sample value Scope Description
@mergin_username martin global Name of the user currently logged in to Mergin
@mergin_url https://public.cloudmergin.com global URL of the Mergin service
@mergin_project_name Tree survey project Name of the active Mergin project
@mergin_project_owner martin project Name of the owner of the active Mergin project
@mergin_project_full_name martin/Tree survey project Owner and project name joined with a forward slash
@mergin_project_version 42 project Current version of the active Mergin project

A common use case is to use @mergin_username as the default value for one of the fields in a survey layer to automatically track who has added (and/or modified) a particular record.