Thank you for the help and detailed explanation. After some work, I agree that the easiest would be to switch out the existing relay. Well, perhaps equally easy with what I ended up doing. I put the Shelly 1 in with the ABB relay working as the switch for the Shelly. A combination of annoyances with selection of AP on the Shelly and some wiring that threw me off in the cabinet caused it to take far longer than I would have expected. Long story short, I used this diagram and inserted the Shelly between 2 and the light using SW and O. Seems to work and the indicators on the switches light up as well.
Thank you for the extensive help. Much appreciated.
Here is the diagram I used.Screenshot_1.png