I have 1 light, that is controlled in a 3-way with 1 Inovelli Red Series Dimmer and 1 dumb switch.
I also have another light in the same room, that is controlled with a single Inovelli Red Series Dimmer.
Is it possible to link both smart switches together so that when you turn them off or on, or dim them it controls both lights?
If you’re using Home Assistant per your profile, I think you’ll find this useful 
Thanks. I’ve done it this way. I guess switch association only works one way between devices? Like I can only have switch A controlling switch B. I can’t have switch B also controlling switch A at the same time?
Gotcha, I believe you can set it up the opposite way as well if I read this part of the thread right -
I’m not as familiar with Home Assistant but I know Hubitat also has something called groups you could work with…maybe there’s a similar feature you can use as well? Then both switches work off the group vs associations? I’ll try and take a look at that in a bit and will update if I find anything.
Oh interesting. Thanks I’ll take a look at that additional parameter.
Thanks @chack . It seems to work. The only thing that seems off is the lights dim at different speeds, even though both the z-wave and switch dimming parameters are set to 3 on both switches.
Do you mean they dim at different speeds as in some dim faster than others, or maybe that some start dimming before others do and so they end in sort of a staggered group?
If the latter, I think you have options based on this thread -
If the former, can you verify the switches are on the same firmware, have the same settings, etc? Are they all the same bulbs for the different lights?
Firmware 1.52 on both switches.
They dim at different speeds when dimmed from one of the two physical switches. For example, I turn them both on via one switch (this now works great thanks!), and then I start to dim them from that switch, the further away switch dims at a faster rate so that light ends up being dimmer.
Not really a big issue at all, because we set the default local dim on all switches based on sunset/time of day. More of just a nice to have.
Going on the settings here: Dimming Speed and Ramp Rate (Parameter1 and Parameter3) are swapped - FIXED IN 2020-08-12 DRIVER - #3 by mamber - Firmware Discussion - Inovelli Community
I have all the lights in my house set to:
Param1 = 1 (fast on/off via zwave command)
Param2 = 3 (regular fading when dimming via paddle switch)
Param3 = 3 (regular fading when dimming via zwave command)
Param4 = 1 (fast on/off via paddle switch)
And between both switches I have Association back and forth for:
2: Basic_Set
4: Switch_MultiLevel_Start/Stop
I’ll try and get some time tomorrow to take a look at those parameters more and see if I can come up with anything else to try. Don’t have an lzw31 myself to compare and I haven’t actually used associations 
I’m pretty certain there’s a way to take care of that though.
I think from reading on it some more, and catching up on that thread that what you’re referencing was actually fixed in a later firmware release and you should have Parameters 1/2 and 3/4 in sync. I’d try doing either -
Param1 = 1
Param2 = 1
Param3 = 3
Param4 = 3
OR
Param1 = 3
Param2 = 3
Param3 = 1
Param4 = 1
And confirm which of the two matches up with your expected behavior.
That is from an old post which I reported a bug in the previous behavior. Like @chack mentioned, it has been fixed since then. If you run the updated Inovelli driver/device handler (2020-08-12 or newer) then the behavior matches these descriptions:
If you included them with security, you will likely have better performance if you include them non-secure. I recommend that if you are using association as you will have the quickest response time.