Use existing dumb switch like an add-on switch for 3-way configurations

I have a 3-way configuration in my house where the location I want to install the Inovelli switch (very central location in living room) does not have line - the line comes into a switchbox that is out of the way and not where I need a smart switch. Diagram of what I have now - black triangles are wirenuts:


In order for me to put my Inovelli Red in the left box, I need to buy an add-on switch which (how I understand it) is basically just a momentary switch so that the Inovelli can detect pulses, and toggle the on/off of the load when it sees a pulse. Then the extra traveler can be used to get line over to the left box to feed the smart switch.

It is unfortunate to have to buy a $20 switch to make that work. It would be really great if instead of detecting pulses, it could detect rising/falling edges so that a dumb 3-way switch (acting basically as a single pole). Basically the traveler screw on the inovelli would be treated as an input rather than an output, and would watch for current coming on/off to decide when to toggle the load.


In this setup both switches would get line in, and the traveler wire would be hot or cold depending on the state of the dumb switch. When inovelli sees the traveler wire change, it would toggle the load.

I’m not sure if there are technical reasons preventing this, but if possible then this would be a great option for people like me to be able to easily install 3-ways where the smart switch location doesn’t already have line, without having to buy an add-on switch.