If you installed Parrot first and then you installed EndeavourOS goe into /etc/deafult/grub and make sure to set
Then update grub
sudo grub-mkconfig -o /boot/grub/grub.cfg
Thirdly make sure to go into parrot and either uninstll os-prober or disable it in the grub menu so that when you do updates in Parrot it doesn’t take over. This way EndeavourOS grub is always controlling the boot.