Display Key & Text in Query Variable F4 Value Help

Hello folks,

my request is fairly simple but I despair to have key and text in the variable F4 help of my query:

In the query, the InfoObject is set to "Key & Text" in the filter section

Also the InfoObject itself and the CompositProvider is set to "Key and Text":

There is also an Aggregation Level involved. As far as I know I cannot set the display variant in the AL, but it is correctly derived from the unterlying Composit:

But there are actually texts available if the user manually sets the values to key & text during query runtime:

What am I missing? How can I display key and text in the variable value help?