Now create a new MIDI region on the same track and select it, and also select the 'template' region. Select all the notes and mute them, and use this as your 'template' for the selected key. Rinse and repeat until the entire top-to-bottom piano roll is marked in that MIDI region. Now, create a MIDI note for each note in the scale you selected. Pick a key/scale in your mind and draw a new, short MIDI region. This only seems to work with 10.1 and up, because you'll need the Collapse View button in the Piano Roll. Logic Pro X has something similar with quantizing to a particular scale, but it wasn't as helpful.so I found a work-around. In the latter, you could select the scale/key you're in, and the piano roll would highlight only those notes for you, making it easy to work with the correct notes.
Here's a Logic Pro X feature that miss from working in Presonus Studio One.