We can use only one value.
Since you have your query string built up already, it will be easy to make $JavaXPathQueryStr have this string
Application = 'PCM' or Application = ‘LMS’
and in the XPath constraint box say
[$JavaXPathQueryStr]
If you want to do this in a microflow, i am afraid you have to do a seperate retrieve for every value and then add the lists together.
Maybe you want to look at the appstore component called gridsearch, which generates the xpaths client side.
Performance is much better and you do not loose the option to sort and page your search results as you would when you would use a microflow datasource (assuming you are not using mendix 8 yet.)