I know how to set custom ringtones, and how to make a VIP list. But I want the phone to ring for everyone except one person, and to be silent or to vibrate just for that one person.
I tried Smart Actions, it has a setting for replying with a text message while I’m at work. But I want it to be silent for one particular person while I’m at work.
I found a bunch of vibrate apps but I don’t want everyone on vibrate, just this one person.
How to do it?
Set the custom ringtone for that person to Silent - if that’s not an option (I seem to recall it being there), then install a silent ringtone. Yes, they exist. 
Another option is to set that one person to go straight to voicemail. It’s a built in option on all the Android phones I’ve had and what I’ve used to deal with wrong numbers that won’t stop calling. As in many calls over many months, not just a few in one day.
I suspect the OP wants the call but wants to be selective and private about when he answers it - e.g. a family call during work hours. Otherwise, there are several ways, including direct-to-voicemail, to block a call.
Thank you, everyone!