White is neutral. Black and red are hot. Red, usually is switched hot.

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?

The white wire that's wirenutted and stuffed in the box, is could be your neutral for a switch on the left. Trace that wire to other boxes if you can to be sure. Make sure it's not connected as the hot on other devices. Does the 3-way switch on the right use the white wire somewhere? That's a clue.

Neutrals are required in switch boxes, but that's a very recent code update. It's equally likely you'll have to run your own neutral.

Traditional, non-electronic switches don't use a neutral because there's no load on a switch. All a switch does it connect or disconnect the circuit behind the switch; i.e: your light(s).

Electronic switches do take a neutral because they carry a load.

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.

OK, do you know what a pigtail is? Make a couple pigtails off the couple white wires that are nutted in the back and take each pigtail to one device. Use at minimum 14 AWG wire, or 12AWG. But take note. That 3-way on the right is using a white wire to carry current, probably as a runner or traveler. Check the other 3-way switch in the room and you'll see it there, too.

This should show you that a white wire is not always a neutral, ESPECIALLY in homes. Ok?

Also, if your smart switch is a dimmer, you ought to turn the circuit off, just in case you haven't done that. Hooking an electronic dimmer up "hot" will kill it with inrush current.

Black is usually hot. Whether it's line or load I can't tell from a picture after things have been removed. Red would typically be going from a switch to an outlet or light. Or whoever did the original wiring ran out of black and used red. It happens.

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.

Making a splice for all your neutrals together is common. You'll also see it happen at a switch where your hot wire forks to feed both a switch and then leaves the box to feed a plug with constant hot. Keep in mind that electricity doesn't care what color the wire is and sometimes the original electrician doesn't care either.

If you really want to know more, study parallel circuits and series-parallel circuits. This is the science behind electrical work. The pigtails coming off a spliced connection is an example of power feeding along "parallel lines."

The switch being "in front" of the lights in a similar circuit is an example of a series-parallel circuit if I recall correctly.

I also recommend you study the difference between single pole switches, 3-way switches, and electronic switches if you can afford the 20 minutes.

It might help you to not think of switches as a device that uses power. The old-style switches (single-pole, 3-way, 4-way) are really points in the circuit that use no power and break the connection. Functionally they are like circuit breakers.

They don't use a neutral because power is only passing through the switch, not being used by it. Electronic switches are different and yes, they use power and a neutral. Neutrals are your return path to the breaker box.

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 completely disdagree! Use a multimeter to determine which is the neuteral wire. Turn off the main breaker and test white to ground for continuity.

That's great!