any other light weight trimming people have?
Essentially, I already use mpv as my video player, which in addition to being very fast also allows seeking frame-by-frame, saving and returning to positions, and running Lua scripts. So I wrote some Lua which reacts to a specific key press by saving the current video timestamp. Press it again and it records a second timestamp, then it fires off Handbrake CLI (FFmpeg could also work) to do the cutting and save the trimmed file.
If you search online for “mpv cut video” you should find some plugins with that same idea. I have never used them so I can’t attest to how good or bad they are. All the ones I found are larger than my approach, but then again I just made mine do exactly what I want without customisation so that’s to be expected.
One specific advice I’ll give, if you go this approach and are on the Apple ecosystem: Use the Handbrake CLI instead of FFmpeg to do the cutting. FFmpeg was super frustrating and I was unable to get a result where the output video worked properly in Quick Look and sending through iMessage; after too long trying to get it to work and messing with a myriad flags, I switched to Handbrake with no weird settings and it’s been working flawlessly ever since.
I'm a big fan of ScreenFlow, but light it is not ;) If you just want to trim and assuming you are on macOS, QuickTime's "Edit > Trim..." does the job. It's what I used before doing the Emacs thingy.
But haven't worked on it in months. Usable for now if you don't need audio
https://en.wikipedia.org/wiki/Shotcut
P.S. What's great about tools like emacs or ffmpeg is their usability via a command line and thus scripting. Which even works on an Android device running inside Termux.