Yes, stringify is in many ways similar to smartrules, I just like the smart rules interface better. Also, I’m not sure stringify can respond to mode changes, and smart rules can.
Back to the use case…
The Smartthings official features are almost all based on an event trigger model. “When X happens,…” The exception is Mode.
So if you want to catch the moment of the event when the door is unlocked and see if that is in away mode, and if it is, blink the lights, you just need to find a feature where door unlocked is an event trigger.
The official smart lights feature doesn’t trigger on a door being unlocked, but it can trigger on a door being opened if you have an open/close sensor.
So it would be easy to set up “if the Mode is away, and the front door opens, turn on the virtual switch.” There’s an event to capture there, which is the moment that the door opens.
Even better, the official smart home monitor feature can trigger on a door being unlocked if you set up a custom alert. So you just set up an alert that is the door unlocked while you are away, turn on the virtual switch.
These two official features work because you were treating the moment that the door unlocks as an event trigger.
If instead, if you want a “do while” that checks to see if the door is already unlocked when the mode changes to away, then you would have to go to either core or SmartRules.