The default start-up directory appears in the top of the Juno window… but where can I change it? Probably, the ideal would be that it starts in the directory REPL was set to the last time I used it.
Open settings via Command-J + Command-, or the Juno > Settings menu. Expand “> Julia Options”. Scroll down to “Persist Working Directory”, check the box, and enter “/Users/x/.julia/dev” or some such into the “Working Directory” field.
(Checking Persist Working Directory only without filling Working Directory does not appear to have any effect. It does not start a new Julia session where the last one ended.)