String ensemble example

It's not clear what you want to do. It is certainly possible to import the MIDI file and to create figures from it. It even recognized them as strings, and by just hitting "Play" I got something very close to what the video sounds like, even with the default sound. You are then expected to use a professional VST of course, if you want a better sound.

If the problem is that you want to assign different lines to different instruments, e.g. for a string quartet, then you need to manually separate those lines, e.g. assigning them to different colors and then using the "Split" option.

If the problem is that you want the exact same notes, then you need to import the MIDI as a take (yellow color symbols) and NOT interpreting the take, which would create Synfire figures, which would of course sound different.

That's a problem regarding the VST. If you have a professional strings VST you can use the expression/dynamics parameters (CC controllers) to obtain a real-life-level sound. Definitely possible in general, and definitely possible with Synfire.

It's very difficult to understand what you're trying to do, you don't explain yourself very well.

Notes/symbols are of course possible to insert; if you want to insert specific pitches (I can only guess here, because it's not clear what's your issue), you can do that via the P / Pitch symbol (the yellow one). Synfire is not meant to write music like this though, for that you can use a notation program or a DAW.

Dear janamdo,

I am also a beginner, hence in last few days had a couple of occasions where I instictively felt some lack of functionality. 
In all cases after careful study of the docu teached me that I was wrong, even I understood that Synfire is built around concepts which I was not even aware of before.

Based on that track record I personally try to ask humble questions to the expert and instead try to keep any statements that "Synfire cannot..." or "Synfire is bad at..." to zero.

Maybe this helps also to keep the excellent discussion style in appropriate mood.

Also I try to explain exactly (and without ambiguity)  in detail, what I have already done in solving the problem, thus help others understand my stake, in order to make sure that theres minmal repetition. Lets help each other.