Noodletrap is definitely not intended to be a piano roll replacement. It’s more like a sketch pad for your musical ideas. You fire it up, start recording, jam out a melody on your keyboard, and then your performance gets captured to a new phrase within the instrument. You can quickly make several different takes to experiment with different ideas. Once you’re done, then you can decide which phrase(s) to keep for your song, edit and tweak them a bit more, and so on.
PS. Since Noodletrap is a 3rd party tool, not a native feature of Renoise, it’s probably better to ask further questions in the tool’s own dedicated discussion thread. I’m sure that danoise, the tool creator, will be happy to assist you.