3mle will normally only put the tempos into one track, but MS2 requires tempos for every track, otherwise they we desync. So if we have the two tracks below:
/*M 0 */ t145>c+8.<b8.>c+8t120e4.t100&e16.r32
/*M 1 */ t145c8.<b8.a4t100g8a8b8
and
/*M 0 */ <<a2>>c+2
/*M 1 */ <c2>r2
So we have 5 tempo changes in track 1, we will need to place those into track 2 (every track in the song if you have more than two). To do this correctly you want to look at the column on the left for track one, it has the time stamps for each event including tempo changes. The 1st, 2nd, and 4th tempo changes are easy, 1st and 4th are at the start of the measure (watch the time stamps! 3ml can't always make the start of measure visible like this, it could be before or after the indicator) so we can just place those in. The 2nd is at time stamp 0.0192, this is exactly half the measure, I recommend playing around placing the tempos until you find the right place, but in this case it is easy because track two has only 1 note that is half the measure long so the tempo can just go after it.
(track2)
/*M 0 */ t145<<a2>>t120c+2
/*M 1 */ t145<c2>r2
Now we just have the 3rd and 5th, these are a little harder because we are going to have to edit notes or rests to get them right. Lets start with the 5th tempo, editing rest is a little easier than editing notes, I like to split everything into 8th notes(or rests) so the r2 becomes r8r8r8r8. Now play around placing the tempo in at different spots until you find the right time stamp, this time it happens to be after the first r8. Now the second measure of track two is: /*M 1 */ t145<c2>r8t100r8r8r8. Now for tempo 3 we have to do the same thing but we need to edit a note, so to split a note we need to add ties (&), c+2 becomes c+8&c+8&c+8&c+8. The ties make it so each of those notes still sounds like its just a single note. Tempo changes will need to go between the note and the tie that follows it, like this c+8t100&. Again play around find the right time stamp, this time it is after the 3rd split note, c+8&c+8&c+8t100&c+8. Now an 8th note might not always be what you need to split rests/notes into, its possible you will need to split into 16ths or even 32nds. Final product is below. Optimizing the track we condense the extra rests we made but not the notes, you will have to manually optimize that if you are short on character count.
/*M 0 */ t145>c+8.<b8.>c+8t120e4.t100&e16.r32
/*M 1 */ t145c8.<b8.a4t100g8a8b8
and
/*M 0 */ t145<<a2>>t120c+8&c+8&c+8t100&c+8
/*M 1 */ t145<c2>r8t100r8r8r8