There’s this as a kcm ofc: System / GRUB2 KCM · GitLab
For Plasma 5 → GitHub - maz-1/grub2-editor: A KDE Control Module for configuring the GRUB2 bootloader. Unofficial KF5 port.
In the AUR → AUR (en) - kcm-grub2-git (no idea if it works, I use systemd-boot).