Integration into an existing multi switch light circuit

[SadruddinW]

I have 3 lights currently operated by 4 switches, (2 2-way,2 4-way). All good so far. 

But. 

I want to add another switch into the system. It looks like a plus 1 mini would be part of the answer, but I'm stumped as to where I go from there. What will the new switch effect? What do I put into the current circuit, and where. 

Sorry if this is in the wrong place. As you can probably tell, I'm new to this smart switch business. 

Any thoughts Greatfully received. 

[Pluto]

Usually the Shelly would be installed between the switch just before the light and the light itself.
Depending on available space and access to the necessary wires, this could be inside the switch enclosure or in the lamp fitting.

Note that you need to have access to the following wires for the Shelly to function properly:

• Live wire (L) - This wire must be permanently Live, so not a switched wire
• Neutral wire (N) - If not present at the switch enclosure, you could attempt to pull a wire from the lamp fitting to the switch
• Switched Live / Signal (SW) - This is the output of the (final) switch, which used to be connected directly to the lamp's Live leg
• Output to the lamp (O) - The Live wire of the lamp that used to be connected to the switch, goes here.

Getting permanent Live wire at the Shelly is often the biggest challenge.
One way to tackle this is to replace the toggle switches by momentary switches, which you wire in parallel.
As a n-way switch has 2 switch wires running between the switches, you could re-arrange them such that 1 of the wires now carries permanent Live and the other carries the switch signal.
Make sure you set the Shelly's Button Mode to Momentary (if you get errors, set Power On Default Mode to On/Off/Restore first) so that a press on the switch toggles the light.