I have two identical devices USB encrypted and mounted. The left hand Dolphin panel shows them as:
7.2 GiB Encrypted Drive
7.2 GiB Hard Drive
7.2 GiB Encrypted Drive
7.2 GiB Hard Drive
I can click on either of the first two lines for the same result and similarly for the second pair (used for backup). Is there any subtle difference?
My main question is: Can any of these names be changed or the icons before them so that I can distinguish between them before clicking on them?
Note the difference is shewn after clicking by the UUID at the top of the window.

Does this touch a chord with anyone!

If you assign labels to the volumes, then those will be shown instead of those generated names.
This can be done using the appropriate file system tools.

Thanks for help. I have tried :
mlabel -n p:Main_data having assigned p: to /dev/sda1 but get response "No directory slot" and

e3label /dev/sda1 Main_data responds with "Bad Magic Number in super-block ...."

I am wondering if the Luks encryption with ext4 puts the key in the slot that the label wants to use?

I now have a solution. A USB flash drive labelled "SpareUSB" with Windows formatting shows the label "SpareUSB" in Kinfocenter and the side panel of Dolphin. However after using "cryptsetup luksFormat" the label is deleted. Kinfocenter says the label is not set and the Dolphin side panel shows name as "xxMiB Encrypted Drive". This, which is not a label, is replaced by a label name provided with the -L option of mkfs when the flash drive is first formatted within Luks. I do not think it can be changed subsequently. Kinfocenter still says the label is "Not set" but inportantly the Dolphin side panel now shows "SpareUSB". Problem solved.

I'm not familiar with how LUKS works and in particular how it interacts with KDE - however if the actual file system is accessible somewhere, the e3label and mlabel tools will probably work against those. If you run "mount" when Dolphin has unlocked the LUKS partition, then you will probably be able to see where the unencrypted partitions can be accessed.

Good to see you managed to find a solution though.

Optimist wrote: This, which is not a label, is replaced by a label name provided with the -L option of mkfs when the flash drive is first formatted within Luks.

I try to do the same, but it doesn't work for me. You mean something like?:
sudo cryptsetup --verbose --verify-passphras luksFormat /dev/sdb2 -L MyLabel

Or you mean that the label created in windows was preserved. Must it be created in windows? (I do that on my flashdrive and Windows 7 is not capable to partition a flashdrive.) Label created by:
mkfs.vfat /dev/sdb2 -n "MyLabel"
won't get preserved?

@bcooksley: The problem is before mount, because you don't know which one to mount.