I’m using both Ubuntu and Manjaro and both Gnome and Budgie (on both distros). So I’m switching between these 4 different setups all the time. I’m also launching wayland once in a while, so that makes 6 (only with Gnome).
My main concern with Budgie on Manjaro is that the Pixel Saver applet is not updated to work like the guys here do it. It’s not maintained either here but at least it’s shipped and it works on UB. But in Manjaro it’s really ugly. I’m using Unite on Gnome, and I was using Unity before. So this has been part of my workflow for 10 years, so if I don’t have it I feel limited.
Now, regarding the issue at hand. It’s sad that @ruwe got impatient. One of the greatest things about Linux is that you can almost always recover an install. Via recovery/fallback, chroot, or via a handy tool that would have gotten all your root partitions (and Windows) to boot.
Make a bootable USB out of it, boot on the USB, and the boot repair thingie just starts automatically when reaching the DE. I played a lot with dual boot (Ubuntu/Manjaro) in the last year on 3 different computers and it has gotten me out of desperate Grub situations several times.
There’s also update-grub, update-initramfs, make-grubconfig and mkinitcpio that can help you rebuild a lost/broken/missing-another-distro-image grub, depending on your distro.
Also, I bought a new laptop lately. And I’m just venting here, but I just copied the partition from the previous 2.5" SATA SSD to the new M.2 NVMe SSD and booted as if there was never a computer change. No new install needed. It might not be the cleanest but it just works. And if it didn’t, I knew boot repair was the backup plan.
That’s how amazing Linux is. You can easily avoid to reinstall most of the time. I might still have an install that went through 3 computers and 3 different drives and it runs as if it was freshly installed.
Grub is touchy, because distros work differently, but there’s always a way.
Even on EFI bootable Live USB, depending on the distro, sometimes, you just copy the content to the drive, and sometimes you need to burn the ISO. IT’s a matter of trial and errors, but eventually you don’t lose or mess anything.