Datasource variable regex with another variable


I have a couple of datasources for every Kubernetes cluster.
For example Prometheus datasources have the same name as K8s clusters (aks-dev1, aks-dev2 etc) and Tempo datasource have names Traces-aks-dev1, Traces-aks-dev2 etc.
The idea is to automatically select the proper tracing datasource depending on what is selected as Prometheus datasource.
I have a variable for Prometheus datasources named cluster. And I’m trying to create another variable called tracingCluster with Variable type Datasource and type Tempo and use regex like /Traces-${cluster}/ Unfortunately, it doesn’t work.
Am I doing something wrong, or it is not possible at all?