Comment by hiccuphippo

Write a text file with all the parts like this:

    file 'file1.mp4'
    file 'file2.mp4'
    file 'file3.mp4'

Then call ffmpeg like this:

    ffmpeg -f concat -i files.txt -c copy output.mp4

And I guess you could make an LLM write a {G,T}UI for this if you really want.