As you have noted, this cannot be achieved automatically through the usual Clonezilla interface. However, it can be
accomplished with manual intervention by following a couple of simple steps documented
on the Clonezilla FAQ page.
For example, how can I restore an image of a partition to different partition,
e.g. restore the image of /dev/sda5 to /dev/sda6? By following the following steps.
Steps to follow
Create the new target partition /dev/sda6, making sure that its size
is equal to or larger than the original /dev/sda5 partition for which you
have a restorable Clonezilla image.
Now, make a copy of the Clonezilla image directory of the original
partition. Here we will use the image "my-image" as an example, e.g.
cp -a /home/partimag/my-image /home/partimage/my-image-new
Now we have to change some files in this new image directory: /home/partimage/my-image-new.
Rename all the file names with the partition location identifier in them
from that of the original partition to the identifier of the new target
partition (eg.: /home/partimag/my-image-new/sda5* as
mv /home/partimag/my-image-new/sda5.ext4-ptcl-img.gz.aa /home/partimag/my-image-new/sda6.ext4-ptcl-img.gz.aa
mv /home/partimag/my-image-new/sda5.ext4-ptcl-img.gz.ab /home/partimag/my-image-new/sda6.ext4-ptcl-img.gz.ab
Next, modify the contents of /home/partimage/my-image-new/parts text file in the
same folder, again replacing the identifier of the original partition
with the identifier of the new target partition (eg.: replace "sda5" with "sda6").
Having made these changes to adapt the image to a new target
partition, you can now attempt to restore to the new and different
partition location. Select the latter, adapted (my-image-new) image from the
Clonezilla repository and the new target partition location using the usual Clonezilla interface and it should now
allow you to restore it to the new partition location (/dev/sda6).
Advanced (expert) parameters, if the two partitions differ in size
There are also some advanced (expert) parameters, again documented on the Clonezilla site, that can help with this if the two partitions differ in size.
In particular, the "-r" option to resizes the file system in the new partition automatically.
Note that to restore an individual partition, you probably do NOT want
to use the "-k1" option which adjusts the partition table, as it adjusts the WHOLE partition table.