The newest versions of Jmeter have a fantastic sampler called “Debug Sampler” that will show you the values for: Jmeter Variables, Jmeter Properties or System properties.
You can insert them wherever you want in the script to get values at a given time. You’ll want to have a “View Results Tree” enabled to view the sampler.
Given that Jmeter declares variables from a file on run, you won’t be able to get your ideal solution.
I’m curious…would it be cleaner to employ “CSV Data Set Config” rather then populating “User Defined Variables” from a properties file?
Edit: Added explanation on variable declaration and asked CSV question.