Seems like a detailed answer to me!
I would use webCoRE to setup your rules. Just as @JDRoberts explained, you will have more versatility using a either Virtual Switch or a more complex rule engine such as webCoRE.
Saying all of that, if you have the GE Plus Switch, you could actually use one of the “Button” features which are double tap up or down.
This is how I would do it in webCoRE:
If Dimmer 1 (Wall Dimmer) changes to on
And
Dimmer 2 (Plug In Dimmer) is off
Then with dimmer 2 switch
Turn on
If Scene X executes
Then with Dimmer 1
Turn Off
If Dimmer 2 changes to off
And
Dimmer 1 is on
Then with Dimmer 1
Turn Off
This way, Dimmer 1 controls the on function for Dimmer 2
Dimmer 2 controls the off function for Dimmer 1
Now, the better way to do this, with the ability to keep the lights independent, is the following method:
Purchase a Smart Button or a Replacement GE Switch that’s the Plus model. Xiaomi make a decent little button for $10 US.
Use a custom app called Trend Setter which will create a virtual dimmer that will keep the lights in sync when turning off/on and adjusting levels.
Then use the Button to Toggle the Virtual Dimmer on/off.
Use the Dimmers independently without compromise.