
I would like to display a different name of these items - that would indicate for example that one is windows partition, other ubuntu, etc.
Is it feasible?
Yes, but not through thunar. Mapping a name directly with partition is something that not even supported by dolphin.
What you should do is add a disk label instead, for linux ones, use tune2fs to set a label, i.e to label the partition /dev/sda1 with Ubuntu (JUST AN EXAMPLE!), you do a sudo tune2fs -L Ubuntu /dev/sda1
For windows one, just boot into your Windows and rename it in My Computer (Press F2 when you selected the target drive, and type in the letter), afterwards, the drive would have a label displayed.
Meanwhile, in a different circumstance, as I was managing partitions in Gparted, I noticed the option 'Label' that could be accessed for unmounted partitions


This label is the one in Thunar's side pane. Any partition, including Windows can be renamed in this way.