Search field syntax: source path/mailbox

I am getting addicted to the search field and the concise syntax with modifiers. I tend, however, to often restrict my search to some specific IMAP folder. Would it be simple to add a modifier for specifying the source path or the mailbox (e.g., "p" for "source path contains")? I know that I can restrict the search to the current folder (with the option key) but this requires first moving to that folder. The menu of the toolbar search field also works but I have so many folders that it is nearly impossible to quickly traverse the hierarchy to select the desired folder. Thanks!