I'm not getting the option to boot into manjaro from the Ubuntu grub

Hello everyone,
I have a drive (240GB) and I have partitioned it as - 60GB, 60GB, 120GB. Before the manjaro install it was 60GB and 180 GB.
I have installed Ubuntu on the first partition 3-4 months ago and I’ve been using it since.
But I wanted to install manjaro on this drive too so I created another partion of 60GB and went ahead with the install using live environment, everything went without a hitch.
After the restart when booted into the said drive I was greeted with the Ubuntu grub but I can’t seem to get the option to boot into the manjaro.

It is an external HDD connected via the USB port. I use it that way because of some portability constraints.

The drive was connected to a Dell laptop (i5-5200u, 920M, 8GB ram) when I installed the manjaro. It has windows 10 installed on the default internal drive.

I’ve tried to be as comprehensive as possible with the details of the circumstances. Please let me know if I did anything wrong or is there a way to get the desired results i.e. getting the option to boot into manjaro from Ubuntu grub.