no, but i use app.zoom.us as workaround

I am also have this troubles even from 500 IU (form or vendor of pills doesn't matter) after that i have massive headache with slow pulse in head and unable to concentrate.

How cut video and save it's fragment without full rencoding?

You can use ffmpeg for this, using "copy" for audio and video, but setting "-ss <hh:mm:ss.0>" for the start time and "-t <seconds>" for the length of your cut beginning from the start timestamp given with -ss.

avidemux can do this as I recall. It can also re-encode video if you decide you need that.