Well I wouldn’t use grub-customizer myself. I’ve seen a few broken grubs, unable to boot issues with it in my time. Grub customizer is a known source of malformed grub configs and is fundamentally a bad idea.
I used it in the past, with ubuntu, but stopped using it when I used Mint, also it messes up the Manjaro specific configs. It might work well in Arch, but I haven’t bothered since my Ubuntu days.
Now let’s play with it…
Let’s start by opening your /boot/grub/grub.cfg.
kate /boot/grub/grub.cfg
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
Given that you read over a thousand posts about this, it’s a shame you didn’t read this… it uses settings from /etc/grub.d and /etc/default/grub
It’s pretty straightforward.
Step 1: maybe backup your grub file for reference,
sudo cp /etc/default/grub /etc/default/grub.BAK
Before editing: kate /etc/default/grub
Find unwanted entries, select, delete, save.
When you’re finished, you must run update-grub.
If anything I’d say it’s the mindset of Ubuntu users that think you must install grub-customizer to do the job which is wrong. If that suits you, then go back by all means. There are many issues with grub-customizer (not least the fact that it needs PPA installation, it isn’t supported by ubuntu either… and the latest version is from 2018).
I loved grub-customiser when I discovered it in about 2011, but now it’s 2021.
This from Mint:
This from Garuda:
Never use Grub-customizer unless you want problems.