Okay - after some testing I got it working. Smart switch and all.

Here's how it's wired.

It's not done 100% correct. The 3-way switch did not have a neutral. It seems the wiring went from the circuit box to the outside switch, with runners and a load line sent to the indoor switch (the one pictured). So to get around that I used the neutral wire for the inside single throw switch.

This is not 100% correct because those two switches are on two circuits. So I have added a note in my circuit box that if you're working on one of those circuits to flip the second and vice versa.

But they are connected and working!

I will try this when I get home from church.

Out of curiosity, as I've been turning it over in my mind, is it common practice to not connect the white "return" wire to a switch and just pig tail them all together as seen in the pic? I have only ever swapped out plugs and both sets of wires connect to the plug.

The three way switch on the right doesn't connect to the cluster of white wires at all, that I can tell.

Edit: my home was built in the 1980s, with the possibility that these switches are located in a converted garage updated sometime after that.

So that I understand correctly - I have three wires coming from one line. White, black, and copper out of three sets; white, black, and red out of a 4th. 4 lines in.

The black is load, white neutral, bare copper is ground.

The red out of the 4th line (no copper on that wire) is my switched hot, aka a runner?