Hi again, last month I proposed an idea for interactively manipulating  
the current query in a tags agenda match (C-c a m, org-tags-view).   
Attached here is a patch against 5.18a that implements this idea.   
It's pretty slick, if I may be so bold!

In a tags match buffer, the prompt will now say, for example:

Headlines with TAGS match: office
Press `C-u r' to enter new search string; use `/;\=' to adjust  
interactively

The extra keys are / (and), ; (or), \ (not), = (clear).  Any one of  
them will bring up another window, much like fast tag selection.  You  
can press one key to select the tag or TODO keyword, and that will be  
added to or removed from the query string accordingly.

So, starting with the query "office", I can hit the keys ";p/N-f" to  
transform it to "office|phone-focus/NEXT", assuming my tags and TODO  
keywords are assigned those keys already.  Like fast tag selection, it  
supports single-key (the default), multi-key (waits for RET), and  
expert (no separate window) modes.

Enjoy.. comments & critiques welcome.
Chris