@Senior_Vagabond it really depends on how deep your box is - some responders might have no issue, but may not be relevant to your situation unless their switch box is the same. 

I have two Kasa Switches in a 3-gang box with a dumb switch between them. I can tell you that it is the volume of wiring in conjunction with the added depth of the Kasa Switches over a 'dumb' switch that creates the issue. 

Your best option might be to consider replacing the box - it is probably nailed to the stud; you have two options really -  a reciprocating saw to cut through the nails or sometimes you can just leverage it away from the stud using the box itself to pull the nails - it makes it a little awkward to remove from the cavity, but if you're careful, you should not compromise your drywall at all. Just be sure you identify all your wires, so you know which is which. 

But once you get the old one free of the stud & out, it is then relatively easy to install an 'old work box' and these are available with quite a large volume/depth. 

Search 3 gang Old Work Box at HD or Lowes or Amazon (site won't allow link) - there is a 3-gang 55cu box available that is 3.7 in deep. Carlon Model B355R

They have amazon but ~ 3x the price!!! 

This Video covers the process pretty well - it is for changing out from a single to a 2-gang but the process is the same. 

I actually used this same technique to install just ONE Kasa switch into a 2-gang box (the other switch was a 'dumb' 3-way - the Kasa for that was located at the other end of the circuit) - however the original box was simply not deep enough to accommodate the wiring AND the Kasa, (it was already a very shallow box for even the std switches) - so I swapped it out, (I did not use a saw, just leveraged it out similarly to the linked YT Video) 

I would definitely recommend this as a good way to go - it is no fun trying to shoe-horn the wiring into the box and this will make your job much easier.