I think it's awful this feature is missing.
I like to use Qlik, have copy single unique ID's into SQL server, that are not fun to type.
When checking a certain row for data quality issues.
I also know a lot of people who use the copy function at my previous work, to copy ID's into their registration system, to look up a certain account.
One option you have is to use the browser dev tools to extract the value from the web page.
This is going to work only if you are using the QlikSense server (not sure if there is a similar option for desktop).
Crtl + Shift + C
hover over the value, and you can copy it
It will work ok for single values.