Just recently found out about this. This is particularly useful in some instances where the case is automatically created but the ASIN in question does not appear in the subject, or nothing at all —i.e. “.”—, making it harder to find it later.
To do this, go to the case and click on the “Edit” button on the top right corner:
I clicked it once (a few weeks? months? ago), but didn’t find any use for it, as I put all the information I need in the subject line when I open a case.
But, as you say, perhaps when a case is created automatically - by a mod or whatnot - then it might be useful.
Although I have found mods themselves to be less so…
This is for us, not for SS, so that we can more quickly find a case using appropriate key words in the subject, instead of the “.” or generic title that’s often generated