How to directly boot on GRUB installed on a specific partition instead of "bios_grub" partition?

Here are the partitions of my SSD:

$sudo parted -l
Model: ATA SanDisk SDSSDA-1 (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name                          Flags
 1      1049kB  106MB   105MB   fat32           EFI system partition          boot, esp
 2      106MB   123MB   16,8MB                  Microsoft reserved partition  msftres
 3      123MB   134GB   134GB   ntfs            Basic data partition          msftdata
 4      134GB   134GB   537MB   ntfs                                          hidden, diag
 5      134GB   852GB   718GB   ext4
 6      852GB   872GB   20,0GB  linux-swap(v1)                                swap
 7      872GB   872GB   1049kB                                                bios_grub
 8      872GB   1000GB  128GB   btrfs                                         boot, esp

On the partitions 5 and 8, GRUB is also installed. GRUB installed on the partition 5 can load Ubuntu which is installed on the same partition or Windows which is installed on the partition 3. GRUB installed on the partition 8 can load Parrot OS which is installed on the same partition and Ubuntu which is installed on the partition 5. When the GRUB partition (which is on the partition 7) is loaded at startup, GRUB command-line appears and I need to manually type some commands to load the GRUB located on the partition 5 or 8 depending on the OS I want to use. I would like to configure GRUB in order to directly have a menu that asks to me which one of the 3 OSes I would like to load. How to configure this?