It’s easy to do this if you think of it the other way around – – rather than trying to delay the motion sensors, just delay arming of smart home monitor.
You can set this up as a daisy chain using the official features.
Lock the door. Have this trigger the goodbye routine.
instead of having the goodbye routine change the smart home monitor armed status, just have it turn on a virtual switch which will act as a countdown timer.
using the official smart lighting feature and power allowance, have the virtual switch turn itself off after one minute. (You can’t set these for less than one minute using the official smartlighting feature. If you really wanted it just to be seconds then you would do the whole thing in webcore instead.)
have another routine which starts when that virtual switch is turned off. Have that routine change the smart home monitor armed status
And there you have it: a one minute delay after you lock the door until smart home monitor is activated.
You can see the details on how to do this in the “how to create a virtual timer for a light” article in the community – created wiki. The difference is that article is about turning the light off, and you instead are going to have a routine automatically run, but the timer procedures are very similar.
There are many other ways to do this. Web core, obviously, or the smart app already mentioned in this thread.
I did just want to point out that if you think of it as a delay in arming smart home monitor rather than anything to do with the sensors themselves it’s pretty easy to set up.
As to why the official smart home monitor doesn’t include an exit delay feature, I have no idea. I asked that question on the first day it was released. But since it doesn’t, you have to choose one of the workarounds.