@PepaBulac
I will say that, for testing purposes, and for transcribing purposes (Example: Importing from midi files), I think Mabillco is a great tool to have, and it far surpasses 3mle in every single fiber of those aspects.
However, I still prefer 3mle for its editing. Even with Mabillco's updates now having a text editor of its own, it is completely barebones and lacking in a lot of important editing features (like search/replace, etc.) to the point where I'd rather use 3mle to do text editing (or, heck, Windows NotePad, for that matter). As well, I absolutely cannot stand Mabillco's UI. But that's just my preference; use whatever you feel comfortable with.
As for the question itself, keep in mind that the base octave at the beginning of scores is Octave 4. I typically type the text symbols < or > to denote octave changes within the score. (< to lower octave level, and > to raise the octave level)
Furthermore, if an octave change is drastic (like, it requires more than 2 <'s or 2 >'s to change to the desired octave), then outright setting the octave level itself might seem enticing. You do this by typing the letter "o", followed by the octave level you want the segment to be at.
Example: If you want to go from Octave 1 to Octave 4, it requires less notes to simply just type "o4" than the number of notes it would take to type in ">>>".
I figure I'd post this now since that question was never properly answered. Hope this helps.