As you've discovered, repeating merge variables are not supported.
Why not use separately named variables, like $$label_Test or $$label_Summary?
If you've got some automated process for filling the $$labels, you could create them using an Evaluate() creating $$label1, $$label2, $$label3.
Expanding on the Evaluate idea, you could use a return-delimited list and use GetValue to extract the one you want into a second variable for display.
Or assign each language a number.
$$coffee_label = choose ( $$language ;'Coffee','der Kaffee','el café','caffe')