Disk Management fails to tweak volume in External HD

Hi, there are guides around if you search for your error message e.g.
The operation is not supported by the object, Diskpart Virtual Disk Service error

The simplest basic idea is- and it would seem ok in your situation- to delete the partition and create a new one.

Great that you're using disk imaging.
Turning to your use of Macrium R and overwriting your image:
1TB seems modest (I assume your laptop has 1 internal disk- no specs on that) - especially as you're only using 1 of 4 partitions for image files.

Here's how I do it.
I have a dedicated 1TB disk for this laptop with 256GB SSD - and a 2TB disk for my other laptop with 2 internal disks.

I don't need to worry about space management- when I create my first image I set up a retention rule as prompted by MR.
This rule automatically manages the space on my backup disk.

I use
1 base image
4 differential images
= 5 possible dates to restore to.

And that is never exceeded on the backup disk - because of the retention rules.

Creating the diff. image is about 4 clicks- because when I created the initial (full) image I created a 'definition file' - defining how the backup is created and where it is stored.

(It's quicker to create a diff. image than a full image).

Note that always overwriting your only image means if something suddenly goes wrong during that - you may have no useful disk image at all. Risky.

If you mean the partition you are saving image files to is different from the partitions where you're saving important files, then deleting the first has no effect on the second, provided you get it right.

And if they are important, I assume you have backups too ....

Yes.