@board4mic 

I am trying to follow the 4 way switch hook up. So when installing the two kasa three way switch do you hook up the white common or is it left out. Looking at the diagram it is not hooked up. Any help would be great thanks

@Carl yes, this is exactly how I'm setting my switch configuration, with one tp-link 3 way switch at the end with the neutral wires, one regular 4 way, and one regular 3 way. I believe this will function fine. 

  @Ant._. I have 1 3 way replaced with a smart switch and it is working on the app. The other 3 way at the other end does not have a neutral wire. If I connect a second smart switch without the neutral connected, will it be able to tell if the light is on or off?

  @xRkYqUz Yes, that's what I'm currently trying to install.  Believe me, the struggle is real!

I need to try some continuity tests, but I think this is my setup.  Between the positioning of the lights, and a 3-way at a dead end, it's driving me crazy.  If anyone has a solution to this I'd really appreciate it.

My instinct is to try the HS210's instead.

  @Augustlion This thread is long enough that it might be time to plug my deep-dive video on this topic here again. It may help you. https://youtu.be/kMT7KUVTELo

  @Chicago_SH hello. Recently installed according to drawing. Left the 4-way switch alone and only added TP-Link 3-way switches on the other two locations. Problem is that when I flip the 4-way switch it turns off the power to one of the TP-Link switches. So I'm guessing the 4-way switch is on the end of the circuit not in the middle. Can anyone confirm if that is probably the case or something else happening?

  @ejayb A 4-way switch won't function at the end of the circuit -- and the Kasa 3-way will suck power from any active line, so it is hard to disrupt their juice. You're probably going to have trace wires with the juice off; but another approach would be to put 1 Kasa in at a time and see how they behave. You might find my video helpful: https://youtu.be/kMT7KUVTELo

  @PatchyFog thanks, got it figured out. Took a multimeter and a few hours of trial and error. Ended up being the 4 way paddle switch from Amazon. The switch pattern is not same sides and the crisscross. It is same sides and then same ends. So I had to put the travelers diagonal to each other. It was an enerlites paddle switch.