examples: history, watch later, liked videos, my videos
reasons:...

1. unnecessary because you can click on libraries and see all the playlist
2. pollutants because I never click on them other than the ones I create
3. disorganize my playlists

Good idea!

Sounds useful and easy to do.
I will check it out :)

Your screenshot was not visible:

Here is a first version:
https://openuserjs.org/scripts/cuzi/Youtube_-_Hide_default_playlists

it's working for me, good work, nice

suggestion: an option to disable/enable show more/show less buttom from youtube playlist to always be expanded
reasons:...

1. it in unnecessary because i always use playlist and have to always click on the buttom
2. pollutants

Re: @LuanRdS19:

sorry, i have noticed that have a similiar option and more others too, nice
https://ibb.co/4PH5zxn

Yes, I have only added options in the menu because it is simple to code.

I probably should write an explanation or put screenshots in the description, then people know how to change the options