Mode scripts are running by calling them as a mode:
rofi -modi "name:script.sh" -show name
rofi -modi "fb:./rofi-file-browser.sh" -show fb
Make sure bc, python or bcalc is installed. Check rofi-calc.sh comments for details.
To show calculator mode:
rofi -modi "calc:./rofi-calc.sh" -show calcor, to show in combination with run mode:
rofi -combi-modi "calc:./rofi-calc.sh",run -show combi