Use the Parameters button down below to add stuff to the (..) part of the command. Looks like you'll want to add string parameters. You might need a variable to hold the message so you can use it in an expression later. I'm not a programmer, so this would be a lot of trial and error for me, but this is where I'd start:
Thanks for the feedback. For clarity, I have no issues using these custom commands, as I simply add the appropriate parameters. What I’m after is having WebCore ask me to enter the appropriate value(s) for the selected custom command, in the same way it happens for standard commands.
You can use custom commands with webcore, but you need to fill in the parameters yourself.
I will chat with @ipaterson if there are improvements can be made on this, but it may get complicated that not all devices describe their commands properly.