How to install UserScripts:
https://greasyfork.org/en/help/installing-user-scripts

The effect of the script:
The Super Chat of YouTube LIVE is listed above the chats as history, and its background color gradually changes by 60 times per second.
This script reduces the frequency to 1 time per second then CPU usage is also much reduced.
I wish YouTube revises such a fool design.

for test
https://www.youtube.com/watch?v=2VdBsB4c3oE

My YouTube Scripts:
https://greasyfork.org/en/scripts?set=361295

Twitter:
@kan####ikaku
#YouTubeLiveCpuTamer