It may help to remember that since SmartThings is a multiprotocol platform, you can use any device that SmartThings views as a “button controller” and have it do what you want. It does not have to be a zwave device because you are not going to use zwave direct association or Z wave scenes.
instead, the button controller sends information to the hub whenever a button is pressed and then the hub sends a command to the end device. So since you already have the relays on your smartthings network, you won’t have to physically touch them again. You just add a button controller and use a smartapp like smartlighting to define what each button means.
This is exactly how the minimote works in a SmartThings system, which is why it can be used to change mode, run a routine, control a group of lights which includes both zigbee and zwave, etc.
The GE remotes, including the wall mount 45631, however, cannot be used in this way because they only communicate button presses directly to other Z wave devices which are within one hop. They don’t tell the SmartThings hub what they just did. So those are actually the worst solution for what you’re trying to accomplish.
The topic that @Automated_House previously linked to, the list of remotes, are all button controller devices In the smartthings context. So you can use any of those just as you would a minimote. Some are designed for wall-mounting.
And as was mentioned, the Enerwave SC7 can also be used as a button controller for SmartThings. The issue with that one for some use cases is that it has to be wired into mains power, typically replacing a light switch. The other ones in the remotes topic are typically battery powered. If you were considering the GE 45631 you should definitely look at the Enerwave SC7.
For example, here is custom code created by one community member that allows a lot of control for both a minimote and an SC7. 