So far Numark has understood with NS6 that dedicated button for opening prepare-section is useful. Something that DDJ-SX and Twitch failed. There's still hope those two, if Serato helps them and give the keyboard shortcut. Since loading tracks to Prepare is ctrl+P, could the opening Prepare be shift+ctrl+P? If it already exists, I apologize.

Free hint: Just give the possibility for mapping and I fix more than dozen of your mistakes by myself.