I had an idea which can be useful for me first

More, another useful function is to concatenate 2 videos files (with audio or not). I know it's possible with ffmpeg but quite complicated.
My goal is take a video file, an audio file, associate audio to video and create a new file and at last, concatenate this new file to another to have a final video / audio file.
Ok, I think FFastrans is more 1 by 1 file software but this soft is so great that i can dream?
Thanks to read me

Cheers.
PS: I must say I speak to concatenate iframe only video file, too complicated with gop video file for sure.
PS2 :I try to put together video and audio with ffmpeg and it's so easy that I'm ashamed to asked...sorry