Knife vs Megabool

In the screen grab I have a model of a USB key I’m working on to get to know Blender. 1 is where I’ve used the default Boolean option and got a nasty cut. In 2 to 4 I decide to use the knife tool to try and create the shape I need. Unfortunately the knife creates edges I don’t want or need (marked by the red circles). The only option is to move the vertices and join them and delete the edge them recreate the faces.

Is there a away to cut between 2 edges and not have the extra edges appear?

Or at least be able to remove the edge without deleting the face?

I did a search and found a post where Heohrer put together a script called Megabool and using the same shape to cut version 1 gave me the result in one hit. This is good but you can’t be using Boolean all the time. Why isn’t the script Herohrer put together the default Boolean tool? It’s much better than the default tool.

Cheers, Kordo.