Toggle between dev and production mode

I am building an Expo app, and I like that Metro builder has an option to toggle between production and development mode. however I was never able to get the setting to work on that one.

my question is. 1) where can I set the stting for that 2) I would like to have a similar way within the app itself to toggle between production and dev end points within the app itself however I am worried that this will mess up the cash and might display incorrect data. what's the best way to do it please?