Is there a reason that we don't allow the multiline flag in the search-replace filter?

[BurningTreeC]

I've stumbled upon a case where I get the text from a tiddler and need to do a multiline regex operation on it
But there's no way to do so and I hacked the search-replace filter a little bit to accept the m flag ... now it works for me

Is there a reason that it's not included in the core?