I made a useless thing:
library watch -s 'path : YouTube' -d-8 --zoom --multiple-playback 64
library watch -s 'path : CityVideos' --zoom -m 64
library watch -s 'path : CityVideos' --zoom -m 3 --hstack
library watch -s 'path : CityVideos' --zoom -m 5
https://github.com/chapmanjacobd/lb/#usage
Playback multiple files at once
library watch --multiple-playback # one per display; or two if only one display detected
library watch --multiple-playback 4 # play four media at once, divide by available screens
library watch -m 4 --screen-name eDP # play four media at once on specific screen
library watch -m 4 --loop --crop # play four cropped videos on a loop