I don’t believe there is any arm/disarm delay available for SHM without some type of custom code (CORE)…or at least I haven’t found a way. If you enter an active alarm area to disarm, it will trigger before you can disarm it, and likewise if you set it while you’re in an active zone, it will arm, and trigger as soon as you move, open. Door, etc.
My solution since our primary entry is thru the garage, was to spend the $35 and put an Echo Dot in the garage, and do the arm/disarm there (I use a virtual momentary switch, not IFTTT). Prior to that, I had a Minimote in both vehicles, (they actually worked outside of my garage), and one “stashed” away in the garage for trusted friends.
I think JDRoberts has posted several time on how to set up the virtual switch, but again it doesn’t offer any native delay.