Selection variables - upload greyed out in Analyzer

Hello,

I'm trying to find out how to upload selection variables via .txt when opening a query/workbook in the BEx Analyzer but the option is greyed out in every single query/workbook.

So my question is: under which conditions can I use that option (I suppose NOT if the variable is supposed to be a single value, right?) and is there any chance that option is just plain deactivated in our system? If yes, where can I change that?

Thanks in advance for every helpful advice I can get.

Anja Gäbler