Help bubble on directories/resource url pages has some hidden diagnostic powers
There's a help icon in the intro section on both the administer - system settings - directories and resource urls pages. It pops up a box that tells you what civi thinks things like
[civicrm.root] evaluate to. This can be very helpful for diagnostic use, but there's nothing suggesting that the help icon has those powers.
I'm thinking it might be more obvious as a button somewhere lower down in body of the page, called something like "Explain shortcodes". Quick mockup: