Cannot concatenate text in JXA
displayDialog returns an object, not a string. When printing an object as a string, it is shown as [object Object]. The object returned from displayDialog is as follows:

{"buttonReturned":"Continue", "textReturned":"your text here"}


Therefore, you need to use the textReturned property of the object. You seemed to attempt this when you accessed the text property of Origin, but since the property is called ‘textReturned’, this didn't work either. For each of the variables where you are printing it in a string, replace


+ '     From \t\t\t\t- ' + Origin.text +'\n'
+ '     To \t\t\t\t\t- ' + Destination + '\n'



with

+ '     From \t\t\t\t- ' + Origin.textReturned +'\n'
+ '     To \t\t\t\t\t- ' + Destination.textReturned + '\n'


In the future when attempting to debug something like this, create a minimal, complete and verifiable example. In this case, just use one displayDialog and observe the value of the variable. (MCVE is something generally required in Stack Exchange questions, and I think this question was pushing that limit providing an entire script.)