How can I display the value of a variable inside a condition? I have created a rule using the Rules UI. My rule is not working, and I need to debug it, displaying the values of my variables inside a condition where I make a comparison.

I see within Rules Actions that I can add a system message, but in condition how could I debug variable values?

Rules debug log doesn't show value of variables.

How can I do so?
Try cloning the rule, and adjust the clone, remove your condition &amp; add a system message action that shows the two variable values you are trying to debug.

BTW, Eventually you may want to install a debugging environment like xdebug. This is likely a longer process than you'd want to tackle for a quick fix. However, if you are planning to keep working in the field, it's incredibly helpful.

You'll find a good start here:
https://stackoverflow.com/questions/7303912/setting-up-xdebug-for-drupal-site