@Carl if i can vote for a 4 way switch option, id like to. I need several 

  @Chicago_SH you only need to put one switch on the power supply end, Right Side on your diagram. If you buy the two unit kit, you have two switches to use in different locations. The 3-Way Dimmers, now that a whole different story. Just got done doing this exact thing. And agree on the kudos for the great gear!

If Kasa made an "official" 4-way wifi switch I would buy them for my house.

  @MrShizzle 

This works for me with HS210 and one 4-way switch. Only difference with the schematics that everyone had posted is that the neutral wire of the hs210 of each ends is connected to the neutral line and to the light. 

Four or five years of community requests and still no product. This is starting to make me think TP Link doesn't want to support the demand of the community and I should consider a different brand. I'd be purchasing a handful today if you had a product.

If you don't want to make a 4 way product, how about an affordable middle switch to control the master? In other words, we'll wire as a 3 way with a middle switch that controls the function of the first including dimmer. This isn't a complicated solution but I do not believe smart actions allows the control of dimming. It essentially just needs another satellite that can communicate over Wifi.

The Kasa HS210 setup SUCKS, due to.....LACK OF INSTRUCTIONS. Plus the cruddy app fails fails fails. Half the time it doesn't detect the device, the other half of the time it won't let me name it ("Operation failed, please try again later"). And these are allegedly "smart" switches? Says who?!?? I call them DUMB switches.

  @septer012 3-way switch works fine at either end of a circuit. A 4-way switch is needed for any in-between switches in the "chain" if you want them to all match. I want mine to all match (plus the little round "nightlight" option in the off state is a nice feature) so I wish Kasa would release a 4-way switch. Kasa, you KNOW such a product would sell, so MAKE IT.

  @Indecision I'm curious did you get the V1 dimmer switches to work? Also how do you add all three switches to the app? When I set up just a normal three way it detected the pair and was done. Does the third one just add to it?

  @judetf How do you get all three to add to the app and work as one switch? I haven't used the v1 version but the v2 version just connected as a pair. I've ordered 2 v1 kits in anticipation I can get this working.