Something I'm still looking for:

A tool on Linux that works offline and can do the very basic video editing that Quicktime X does on macOS. Mostly just trimming.

I don't want to create a project, import media, etc. I just want to open the source file, drag that start and end point around, and save a new video file.

Handbrake comes pretty close but it doesn't have visual editing. You have to enter timestamps or frame numbers manually.

Any suggestions?