The Problem here is that zwave local scene controllers just don’t work well with SmartThings. There is quite a bit of discussion in the forums about the what it takes to get them set up and included. But honestly, you’re better off just using a regular no load auxiliary switch designed for virtual three-ways if that’s all that you need it for. The following is popular and works well with SmartThings.
https://www.amazon.com/Gocontrol-Z-Wave-3-Way-Accessory-Switch/dp/B00EAY3K5Y
I’m tired today, so I don’t really want to go into a whole lot of detail, but the point is that a local scene controller is designed to bypass the hub. But once you go to a smartphone app, you really want everything to communicate with the hub so that the App status will stay up-to-date. With a switch designed to be part of a virtual three-way, the switch talks to the hub then the hub talks to the master and everything stays in sync.
If you do want to continue with the VRCS1, the community – created code for the VRCS4 will also work with it, you just don’t have four buttons. ( this is a clickable link) But honestly, it’s one of the more difficult devices to use with SmartThings, and it doesn’t sound like you need it for your particular use case.
Also, before I forget: the minimote is no longer required To do associations. Nor do you need any other physical device. All you need is zwave tweaker DTH. Add your mainspowered device, in this case your auxiliary switch device, to the smartthings network. Then use the IDE to change it to the DTH for the tweaker, set the associations however you want them, and then change back to your regular DTH. The associations are saved in the firmware of the device, so they will remain the way you set them with the tweaker. 