Hi. I’m looking for some advice.
My parents want to control their 3-way LED (18W total load) lights with automation but do not want to change their dumb switches. In US with V3 hub.
Is there a relay or other option that anyone can suggest that would work?
I’ve looked at several relays but was not able to determine if they can keep the current switches or if a momentary is required.
Ignore my previous answer, I misunderstood and thought they only wanted to keep the dumb accessory switch.
To keep the master switch as well, look at the aeotec nano dimmer, it does not require a neutral wire. It works well with smartthings and can be used in a three-way configuration. You may need to also purchase the bypass if the load is too low and you get flickering.
The only thing is I believe you will only get on/off from the accessory switch, not dimming.
@JDRoberts do you know if this needs to be installed behind both switches, just 1 switch or at the light for 3-way no-neutral with a traveler?
The description was unclear and customer service just kept telling me to call an electrician.
It all depends on how the existing switches are wired, so the first step is to map the existing circuit. Since it sounds like you haven’t done that before and probably don’t have the tools to do it, calling an electrician is not an unreasonable suggestion.
There are at least 8 different ways to wire a dumb 3 way, and that impacts how and where you add the smart relay, which is why all of this matters.
And you would have to be physically present to do the mapping to figure out which of the 8 ways applies to this particular switch and I don’t know if that’s convenient.
If you read the following FAQ, it has a discussion of these wiring issues. If after reading that you decide this is something you’d like to pursue yourself, we can discuss it further. And if nothing else, you’ll be in much better shape to discuss what you need with an electrician. 
The topic title is a clickable link. Note that the examples are specific to GE, so it’s not one to one for what you’ll be doing, but the concepts and discussion of existing dumb wiring should be helpful.