Thanks for the reply. There’s some subtlety to the question based on the context of the original post.
In the original post, you mentioned that the presentation side of things didn’t work within the automations (routines) part of the SmartThings mobile app.
What I’m wondering is if you could define the capability with a command that supports multiple arguments (and leave the presentation as single argument). This way the capability defines the extra (optional) argument, then in the Lua code you could implement it as optional. The idea being that from a presentation perspective, it would still be seen in the SmartThings Routines as a single string argument, whereas advanced automation tools that use the capability can choose to send the second parameter.
Happy to discuss more via PM or to coordinate a test of this if you’d like. 