Although I haven't tried them. Cineplay, MPEG Streamclip and Lossless Cut should all support trimming and rewrapping without re-encoding.
Of the three. Lossless Cut appears to be the most robust. It is built to use FFMPEG. MPEG streamclip is dependent on Quicktime and no longer in development. Although it should work with Quicktime X installed. Although Cineplay is supposed to support it. That doesn't appear to be the primary function.
As Lossless Cut seems the best bet. I'd start there. It is open source. So it may have a steeper learning curve. It supports the widest range of video formats.
About:
https://github.com/mifi/lossless-cut
Downloads:
https://github.com/mifi/lossless-cut/releases (The Darwin version should be for Mac)