How to move working installation to another partition

[mjtux]

I have MX 18.2 installed on a 5+ year old Samsung 840 EVO ssd and would like to move the installation to a new M.2 NVME drive.
Both drives have prior installs of Mint.
All of my drives have GPT partitioning and the installs were done for UEFI.
The Mint GRUB installation on the NVME is the primary boot manager.
I tried a new install on the NVME from a flash drive using a snapshot, but the GRUB menu got really messed up.
I got disgusted, deleted the new partition and restored the previous GRUB menu.

Currently, all of the installations are working very well.
The "move" instructions I've found each have some issue, like being for legacy installation instead of UEFI/GPT.

What is the best method for making such a move?
Can you provide some instructions?

Thanks!

other notes:
I have Timeshift installed with each distro and configured for regular backups to an internal hard drive.
There is no Windows on this machine.
There are symlinks for /Documents, /Pictures, /Downloads and some Pale Moon config files on a NVME /data partiton.
If for some reason those symlinks don't transfer properly, I think I can fix that without much trouble.

[fehlix]

The Mint GRUB installation on the NVME is the primary boot manager.
I tried a new install on the NVME from a flash drive using a snapshot, but the GRUB menu got really messed up.
I got disgusted, deleted the new partition and restored the previous GRUB menu.

Not clear, what a messed up GRUB menu look's like, but if you want to keep Mint's as the primary GRUB boot loader,
you would just need to select the PBR (partition boot record) of the MX installtion as a GRUB target during the MX installation.
This would not change anything within Mint's grub. After rebooting into Mint and regenarting the GRUB menu within Mint,
you could select MX Linux from within Mint's menu.

[mjtux]

Not clear, what a messed up GRUB menu look's like,

There were duplicate entries. Grub Customizer showed many unselected leftovers.
After one install, the MX selections were within a Mint 'Advanced Options' sub-menu.

...but if you want to keep Mint's as the primary GRUB boot loader,
you would just need to select the PBR (partition boot record) of the MX installtion as a GRUB target during the MX installation.

Thanks.
I did not know what PBR was.
With the previous install, I did not install GRUB with MX and just let Mint update-grub handle it.
That worked out OK.

This would not change anything within Mint's grub.
After rebooting into Mint and regenarting the GRUB menu within Mint,
you could select MX Linux from within Mint's menu.

That's how it has been.

The snapshot install had a couple of minor issues.
So, I deleted the partition, created a smaller /root and a separate /home partition.
After that, I formatted the /root and did a fresh install with the downloaded ISO, keeping the existing /home.
I installed GRUB on the PBR, but it is not being used.
I did lose the 'memtest' entry and there is no "Options" sub-menu for the SATA MX installation.

Otherwise, it is all working very well.
I now have the previous Mint and MX on the Samsung SATA, and new installs for both on the NVME.
Having the separate /home partition was a major advantage.
That made things much easier.
That was my first experience with how helpful that can be.