Smart Home Monitor doesn’t have any “modes.” Modes are a completely different thing.
The default SmartThings modes include Home, Away and Night, but you can change them or add more as you like.
Smart Home Monitor has three armed states: Armed Away, Armed Home and Disarmed. You can’t change them or add more.
https://support.smartthings.com/hc/en-us/articles/205380154-Smart-Home-Monitor#Configure_Main
A lot of people get confused about this, even some of the marketing people for SmartThings, but it’s helpful if you can keep them straight.