Multi-boot with Grub2 - looking for suggestions

Like many of us, Grub2 is a new experience worth mastering or at least understanding (I think).

On my test system I have two hdds, sda and sdb
Drive /dev/sdb, specifically partition /dev/sdb1 is mounted /home
Drive sda has the following partition setup


   Device Boot      Id  System
/dev/sda1   *        83  Linux
/dev/sda2             82  Linux swap / Solaris
/dev/sda3             83  Linux
/dev/sda4             extended
/dev/sda5   *         83  Linux

I originally installed 12.2 on /dev/sda3, with /dev/sda1 as /boot and /dev/sda2 as swap

I later added a second install of 12.2 on /dev/sda5, then changed it to Tumbleweed.
As installed, the tumbleweed /boot folder is on /dev/sda5.
Tumbleweed has a unique user on the /dev/sdb /home drive.

I now realize I am not sure how to best manage Grub2.
Since Tumbleweed changes frequently, as intended, it seems I will have to keep going back to /dev/sdb3 12.2 to reinstall the new grub2 menu ( I have been using PTA’s updategrub) whenever there is a kernel change or other event that creates a new initrd.

Its is possible (advisable?) to use the /dev/sda1 boot partition with both 12.2(/sda3) and tumbleweed(/sda5) and have whatever is running prepare the new grub2 boot menu in /boot?

I have seen folks showing systems with multiple distributions setup for multiboot, so now wonder “How They Do That?” with respect t bootloader management.

Ideas or pointers to best practices?

Thanks.

I do something similar
I just decide which OS I want to use to manage grub and when booted in it run

grub2-mkconfig -o /boot/grub2/grub.cfg
grub2-install /dev/sda

where sda is my first boot device

never fails

For anyone using the new Grub 2, I have a bash script you might find helpful you can find here: GNU Grub2 Command Help/Config Editor - Version: 1.85 - Blogs - openSUSE Forums

Thank You,

I would let first system load grub2 of the second system and each have own menu.