In Magento's admin there is a section of developer tools. The tool called "Template Path Hints" actives labels in the view identifying what templates load which blocks.
Switching template path hints on/off is extremely useful for theme development. Much more useful and efficient than searching the entire codebase for an element class, id or random string from the rendered HTML in hopes of finding what FTL controls a block of code.
If no comparable tool exists, please add it to your requested features wishlist.