Huh? Click button, record video, "file" appears in the bottom corner of the screen, drag that into Slack or the Github editor, done. I would be worried about the links expiring, is Loom really hosting arbitrary unlimited sized video content forever for $12/mo? Damn, it's a good thing they got bought.
With loom you can edit it quite easily. I currently use Kap (on MacOS). Tool quality it not as good as Loom. Needs more maintainers I guess.
For me, something like Loom without the online-first approach would be nice. It doesn't exist. I searched. Screenshot tools are a solved problem, screen capturing isn't.
After a screengrab with quicktime you just > edit > trim and then save as. Transcripting audio and summarizing would be nice creature comforts but I'm in the "billion dollars for what now?" camp.