Unless I misunderstand how macro builder works (very new to me, didn't use it seriously yet), I suggest that it contains a sort of "projected" caret (note the green vertical extra line on the attached mockup) to better indicate which portions of other file names are affected by the edit. Especially useful when lots of files and scrolling.
Yes good idea! I had been thinking about something like this during development, and your suggestion spurred me into adding it 