Variable with value mappings

I have defined a variable. Example $belegeRezept.

If I set this is the title field of a dashboard the value shows up.

However it does not seem to work with value mappings.

Example Value mappings: type:
Value to text
1 $belegeRezept

The text will be shown as $belegeRezept and not the variable value

Are variables supported for value mappings?