I am using Mac OS El Capitan on my macbook pro and have just installed Power Manager following your recommendations elsewhere on this website (see Low Battery Alert for Mac OS X El Capitan).
However, I see only an option to power down the computer when the battery charge falls below a specified level. I would like to simply display a pop-up warning on the screen along with a sound alarm and, if continued unheeded for a few minutes, put the laptop to sleep instead of powering down. I guess the way to achieve this would be a script; could you send me such a script indicating wherever I have to insert my preferred parameters? Thanks.