For example, we have a Rest Service with two request parameters: firstName and lastName. To merge their values you should create the following mapping: map firstName to localStorage variable "firstName", and lastName to Label component.
In the line with Label component click "Add JS" and paste the following code:
codevar fullName = localStorage.firstName + " " + value;
return fullName;/code
So, in Label will be displayed response parameter firstName and lastName separated by space.