Save command in variable

I created a  Action workflow and I want in fields "command" not to write a specific command, but to write a variable (something about @example) so that the command entered by the user entered it and I could process it further.

That is, I want to read the entered command, change it and execute in my function.

Is this  possible? 

For example:

exports.rule = entities.Issue.action({
title: 'User_command',
command: "State Testing", //In this place I want write don't command, 
//but some variable, @a 

guard: function(ctx) {
return true;
},
action: function(ctx) {
var issue = ctx.issue;
//here I want to handle this variable, @a },
});

If user input in Command Dialog 'State In Progress', then a = 'State In Progress'