Message to logged in users.

Apologies in advance if I’ve posted this to the wrong thread. I spent an embarrassingly long amount of time trying to find where the message for logged in users is located. The default when someone logs in via the WordPress login panel is “You are already logged in.” which I would like to change to a longer and more welcoming message. Problem is I can’t find it anywhere! Did an advanced find/replace though all 3000 some files that make up the website, and now I’m wondering if it comes from the SQL database or what…can anyone help? Thank you so much in advance! Just trying to find and alter that message!