If you install KaOS in UEFI using default settings, you do not have grub.
If you are very sure you have grub, do you have only one OS (KaOS)?
Otherwise the other OS will not appear in your menu and you will have difficulty booting them up.
Anyway, if you install only one OS, the default will make the menu hidden.
So be very sure of these things before carrying out procedure for hiding grub menu.
To hide grub menu, go to /etc/default/grub, uncomment/make following lines to
GRUB_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT=0
Then
sudo grub-mkconfig -o /boot/grub/grub.cfg
at the terminal.
ps: GRUB_HIDDEN_TIMEOUT could be deprecated, but GRUB_TIMEOUT=0 should do the trick.
To adjust systemd-boot, go to loader.conf and add
timeout 0
Again, I'd caution against this. You may not be able (or quick enough) to edit parameters if you have to.
As for tomahawk player, as you were told earlier, please create another topic.