Can you translate it? The instruction is in German.
Not a problem, the browser translates for me (probably most modern browsers can); thanks.
I just used that method and worked fine.
Don't make it too short so that you can enter grub when there are (boot) problems or you want to boot another kernel.
Thanks for the tip! I read that one might be able to pressshift or esc during boot to force grub menu to show up & stay, but it may not be reliable.
I should have done more searching on this forum - what I asked has already been answered (searching for "dual boot change order" for ex).
It's good to know next and so can also just search all over the web for ubuntu or even linux answers:
For reference, I'll add here some other ways I read about:
Some say that using a fixed line idex (like 0,1..) here is not so reliable as the number and order of menu entries may be overwritten on updates and so could be better to either set the default to the id /title of "menuentry" (which should be found in /boot/grub/grub.cfg ), OR, simpler, to the last user chosen entry, like this:
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true
There's also "grub-customizer" GUI app, but some warn it can mess up grub files/settings.
Finally, there is apparently a way to make another installed Linux OS, other than the last installed, hold the main Grub, and it would make it's entry be at the top at the boot menu. I guess it's important if one plans to delete the last installed Linux OS.
https://easylinuxtipsproject.blogspot.com/p/grub.html#ID6