While ffmpeg has editing capabilities it is not specifically designed for editing, and it does not work like an NLE; it takes input(s) and produces output(s), instead of doing non-destructive edits on multiple source files.
Melt however, based on the mlt framework which powers kdenlive, is designed as a
"powerful, if somewhat obscure, multitrack command line oriented video
A melt command can do the same job as the timeline in a NLE. Here's an example from their website that plays an edited collection of shots from the source files a.dv, b.mpg and c.png:
$ melt a.dv in=50 out=100 b.mpg out=500 c.png out=500
There is also the capability add effects, and you can also create edits as XML files.