I was wondering if sheet music could easily be replicated on LMMS because once I get good enough at reading sheet music, I would just love to do LMMS remasters of the Kingdom Hearts Soundtrack. I also have a violin and am currently saving up money for lessons. One thing that I noticed is that LMMS goes by C1, C2, C3 etc. in terms of notes instead of EGBDF. Even though my music needs a LOT of work, I love using LMMS because it's fun to make music.
LMMS does not have music notation and I doubt if it ever will (though I may be corrected).
So if you're saying that you'd like to enter tunes in standard score notation and get them played in LMMS then the only way I know is to use a program like MuseScore or Anvil Studio (both free), You can enter the music in them, export it as MIDI and then import the MIDI into LMMS to play it with the instruments of your choice.
But most people just learn to use the Piano Roll instead. Many of the top producers can't even read those funny dots never mind writing them .
Steve