Many people (including me) have been requesting better filters in Firebug -- in various tabs, including Net -- for years. So far we're still waiting.
It would also be helpful if some of the filters that do exist actually worked well. For example, I can use Firebug's regex filter to search for items in my main (long) JavaScript file... but it seems to work erratically, mostly just finding strings in comments rather than identifiers like variable names. Even worse, the comment strings are shown in gray text overlayed by a gray selection tone that makes them completely illegible, and if I click off the found text in an attempt to make the gray selection tone go away, the whole found string disappears and I jump back to the main text area. Has anybody ever found any of Firebug's search filters useful? Am I doing something wrong?