Speedcrunch is a different product. You can't edit the "notepad", you just interact with the input box which is separate.

I love Speedcrunch and it's an integral part of my Windows workflow, but not as flexible as Numi or Soulver. I would incorporate either of those two into my Windows workflow if they were available as such with the same responsiveness and footprint.

For Windows you might want to checkout OpalCalc. The website is horrible, but the product is actually good (if ugly).