PPM 5.0: dashboard & target into nonSAP-development

Dear Experts,

does anyone know how to specify a target in the Dashboard?

Via customizing column-linkage can be activated so as to jump from a dashboard element into a proprietary development. In the dashboard settings the linkage to EXTERNAL_ID has been activated, however, how to specify the actual target remains unclear.

I'd appreciate your input very much.

Many thanks.

Angelika