How to add Mac os x entry on Grub

Hi,
I am installing Manjaro KDE on my old Imac (after installing it on my 2008 macbook without too much trouble :wink: ).

I would like like to add the os x entry on each start of the Imac because other people are using the Imac.
I donā€™t know how to do it and I donā€™t to make errors.
I send to this post a screenshot to show the actual situation.
At each restart , manjaro boot directly without showing the menu.

Thanks for help and stay safe;

Hi,

I have found a workaround :

I restart the Imac
I select Mac os drive to boot mac os sierra
I start pref system and select mac os hard drive for the starting drive and reboot.

Each time, the Imac start on mac os

to boot on manjaro, I press ā€œaltā€ when booting and manjaro start without problem